Growing Up: Life Stages and Puberty

You have changed a lot since you were born. A life stage is a broad part of life with similar changes in the body and abilities.

Six stages of life

These age boundaries are approximate. A birthday does not switch all your abilities at once. People learn skills at different times, too.

Puberty is the time when a child's body changes into an adult's body. It happens during adolescence. A teenager is aged 13–19, but adolescence can start earlier. Someone aged 11 who has started puberty is an adolescent, even without a teenage birthday.

Order a family photo display

Imagine photos labeled “a newborn,” “a 6-year-old,” “a 2-year-old,” “a 16-year-old,” “a 42-year-old” and “a 79-year-old.” First, find the youngest person: the newborn. Next comes the toddler, then the child. The adolescent comes before the adult and older adult.

The order is baby → toddler → child → adolescent → adult → older adult.

Humans follow the mammal life cycle: birth, growth, adulthood, possible young of their own, old age and death. Puberty makes the body able to reproduce, meaning have young. Becoming able to have children does not mean someone is ready to care for a child.

Doing more for yourself

As you grow, you take on more jobs. A toddler might put toys away. You might pack your lunch or feed a pet. Later, you manage more homework and personal care. Adults often care for others as well as themselves. People still need help at every stage.

Growth means an increase in body size. You grow especially fast as a baby and again during puberty. Between those times, height usually rises more steadily. Adults usually stop growing taller by their late teens or early twenties.

Size and shape change together

A typical newborn is about 50 cm long (20 inches) and weighs about 3.5 kg (7.7 pounds). Many babies triple their birth mass in their first year. For a 3.5 kg baby, that would be about 10.5 kg (23 pounds). Length often grows by about half, reaching about 75 cm (30 inches).

Your proportions are the sizes of body parts compared with one another. A newborn's head takes up about a quarter of body length. An adult's head takes up about a seventh to an eighth of height. The head grows, but the legs and rest of the body grow much more.

Find the gain between measurements

A growth record follows the same person over time. Here is Maya's record:

To find a year's growth, subtract the earlier height from the later one.

• From 8 to 9: $133-128$ gives 5 cm.
• From 9 to 10: $138-133$ gives 5 cm.
• From 10 to 11: $144-138$ gives 6 cm.
• From 11 to 12: $152-144$ gives 8 cm, about 3 inches.

Each gap is one year, so you can compare the gains. The final year has the biggest gain, showing a growth spurt. Across all four years, Maya gains $152-128$, or 24 cm.

A taller person is not always growing faster. You need earlier and later measurements to find growth. Friends of the same age can have different heights and growth spurts.

What changes in old age?

Hair makes less color and may turn gray or white. Skin becomes thinner and less stretchy, forming wrinkles. Bones can become thinner, muscles can lose strength, and hearing or eyesight may weaken. Cuts often heal more slowly.

These changes differ between people. Staying active helps slow muscle loss. Good food and activities that keep the mind busy can help older adults stay independent.

A baby mammal grows inside its mother before birth. That time is called gestation. The gestation period is how long it lasts. In humans, we usually call it pregnancy. The baby grows in the uterus, also called the womb.

Start the count in the same place

Human pregnancy lasts about nine months. Doctors count about 40 weeks, or 280 days, from the start of the last period. This count begins about two weeks before the baby starts growing.

The baby's development lasts about 38 weeks, or 266 days. Animal gestation tables count from the start of development. Use 266 days for humans when comparing those times.

Individual pregnancies vary; horse pregnancies commonly last about 320–360 days.

Work out two kinds of comparison

“How much longer?” asks for a difference. An elephant's gestation is about $650-266$, or 384 days longer than a human's.

“How many times as long?” asks for a division. A human's gestation is $266÷20$, or 13.3 times a mouse's. That is about 13 times as long.

Check that both times use days before calculating. Comparing 38 weeks with 20 days directly would mix units.

Spot a pattern without losing the exceptions

Bigger mammals tend to have longer gestation periods. Compare a mouse, a horse and an elephant in the table. But size does not set an exact gestation time. A hamster is bigger than a mouse and has a shorter gestation.

A red kangaroo is another exception. Its tiny newborn reaches the pouch after about 33 days inside the mother. It keeps growing in the pouch for months. That time after birth is not gestation.

A foal can usually stand within an hour or two of birth. Human babies still need years of care after a long pregnancy. Long gestation does not always mean a baby can do more by itself.

A chick grows in an egg outside the hen's body. That time is incubation, about 21 days for a chicken.

Puberty is the time when a child's body gradually changes into an adult's body. By its end, the body can reproduce, meaning it could make a baby. Puberty starts when the brain sends signals that begin the changes.

A range of starting ages

Girls often start a year or two earlier than boys. These ranges describe starting, not finishing. Puberty takes several years, often about four. Hair, height, skin and other changes arrive gradually.

Genes help shape the timing, so similar timing can run in families. General health matters too. You cannot choose a starting date or speed up puberty by wanting it.

Friends have different timetables

Leila and Rosa are both 11. Leila has started developing breasts. Rosa has not noticed that change. Both starting times can fit the usual range. Leila's changes do not create a deadline for Rosa.

Even the order can vary. Breast buds are often the first female change. Testicles growing larger are often the first male change. Someone may notice new hair or faster growth first, though.

There is no prize for starting first. Starting later within the usual range does not make someone less mature in their choices or less capable at school.

Puberty and adolescence

Puberty describes changes in your body. Adolescence is the wider time of growing from child to adult. It also includes new feelings, changing friendships and learning to make more choices.

For example, growing taller is a physical change. Wanting to choose your own clothes is part of growing independence. Both can happen during adolescence, but they describe different kinds of change.

When to ask about timing

Tell a parent or caregiver and ask a doctor about changes that start before age 8 in a girl or age 9 in a boy. Ask too if breasts have not begun developing by 13, or testicles have not started growing by 14. A doctor can check how the body is developing and answer questions.

During puberty, every body has a growth spurt, new body hair and more active sweat and oil glands. Voices deepen too. You may also feel hungrier, more tired or more aware of your feelings.

Growing quickly

A growth spurt is a time of fast growth in height. During the fastest year, many young people grow about 8–10 cm, or 3–4 inches. Hands and feet may grow first. Shoes can suddenly feel tight, and moving a changing body can feel awkward for a while.

Gaining weight is a healthy part of puberty. Longer bones, bigger muscles and changing body shape all add weight. A growing body needs energy, which helps explain a bigger appetite.

New pubic hair grows around the genitals, the body parts between your legs. Hair also grows under the arms. Hair on the arms and legs may become darker and thicker. The amount of hair differs from person to person.

Why sweat starts to smell

Sweat glands make sweat and become more active during puberty. Fresh sweat has little smell. Bacteria living on the skin break it down and produce body odor.

For example, after a warm afternoon outside, your underarms and shirt may smell. Washing removes sweat and bacteria from the skin. Changing into clean clothes removes the sweaty fabric next to it.

What causes pimples?

Oil glands make oil, called sebum, that helps protect skin. During puberty, they make more of it. Hair and skin may look greasy.

A pore is a tiny opening in the skin. Oil and dead skin cells can block a pore. Pimples, blackheads and whiteheads may then form. This skin condition is called acne. It can affect the face, chest or back, with a few spots or many.

Acne does not mean someone is dirty. Scrubbing harder will not fix the extra oil production. Gentle washing helps care for the skin without irritating it.

A changing voice and energy level

Your voice box, or larynx, grows during puberty. That makes your voice deeper. The change is usually much larger in male bodies, but female voices deepen a little too.

Growing uses energy, so you may need more food and rest. Stronger feelings and a greater wish for privacy are also common. You can learn ways to manage them while your body changes.

Correct body-part names help you explain a question, itch or pain. Genitals are the body parts between the legs. They are private parts, and they have ordinary names just like knees and lungs.

Parts in male bodies

The penis is an outside body part. Behind it hangs the scrotum, a bag of skin holding two testicles, also called testes. During puberty, the testicles begin making sperm. These tiny cells are needed to make a baby.

The urethra is the tube that carries urine, or pee, out of the body. In a male body, it runs through the penis.

Parts in female bodies

The outside parts together are the vulva. They include folds of skin called the labia. There are separate openings for urine and for the vagina.

The vagina is a stretchy tube inside the body. It leads from the vulva to the uterus, or womb. The uterus is a hollow, muscular organ where a baby can grow during pregnancy. In an adult, it is about the size of a pear.

Two ovaries hold thousands of tiny egg cells, also called ova. During puberty, the ovaries begin releasing eggs, usually about one a month.

The female urethra has its own small opening in the vulva. It is separate from the vagina. Urine leaves through the urethra. Period blood leaves through the vagina.

Match a name to a job

Suppose you read “the bag of skin holding the testicles.” Start with the job: it holds the testicles, so the name is scrotum. The testicles inside have a different job: making sperm.

Now read “the organ where a baby can grow.” That is the uterus. The ovaries hold egg cells, and the vagina connects the uterus to the outside. Nearby parts can do very different jobs.

Use clear names when asking

The word “vagina” is sometimes used for the whole outside area. The correct word for that area is “vulva.” Knowing the difference helps you say exactly where something feels sore.

You can say, “I have itching on my vulva,” or “I have a question about my testicles.” A parent, caregiver, nurse or doctor can help you understand what is happening.

Female puberty often begins with breast buds. These are small, firm bumps under the nipples. They usually appear between ages 8 and 13 and can feel tender or itchy.

Changes take time

Breasts grow over several years. One can grow faster than the other for a while. Breasts come in many sizes and shapes. A bra or soft crop top is a choice for comfort.

Pubic hair and underarm hair begin growing. Hair on the arms and legs may darken. The growth spurt often comes early, around ages 10–12. Hips widen, and the thighs, bottom and breasts gain fat. These shape changes are a healthy part of puberty.

A common order is breast buds, new hair, faster growth, wider hips, discharge and the first period. Different changes can overlap. Sweat, odor and pimples can appear at different points along the way.

Discharge before periods

Many girls notice clear or white fluid in their underwear. This is vaginal discharge. It often begins about six months to a year before the first period.

Discharge is a normal body change. Tell a parent or doctor if it itches, smells strong, or is green or gray.

What begins inside the body?

The uterus lining begins building up and breaking down in cycles. Blood and tissue leaving the uterus through the vagina make a period, also called menstruation.

The ovaries also begin releasing eggs. A period can happen without an egg being released, especially in the early years. These are linked body changes, but an egg is not released in every early cycle.

The first period usually starts around age 12, often two to three years after breast buds. If it has not started by 15, or within three years after breast buds, tell a parent and ask a doctor.

Does a first period mean growth has finished?

Nadia has her first period and thinks she must need her final shoe size. A first period does not mean every change has ended. Growth in height usually slows afterward, but most girls grow a few more centimeters. Breasts and body shape can keep developing too.

Male puberty usually starts with the testicles growing bigger, often between ages 9 and 14. The scrotum's skin gets darker and thinner. Later, the penis grows longer and wider.

Hair, height and voice

Pubic hair starts growing near the penis. Underarm hair follows, and facial hair often comes later. Some people grow more chest, arm and leg hair than others. Shaving is a choice; new hair does not mean you must shave.

The growth spurt often comes around ages 12–15, later than in female puberty. Shoulders and the chest become broader, and muscles grow bigger.

As the voice box grows, your voice may jump between high and low sounds. This is called voice breaking. It can sound like a crack or squeak. The voice settles into a deeper sound as the change continues. The growing voice box may show as a bump on the neck, called the Adam's apple.

Sperm, semen and ejaculation

The testicles begin making sperm, tiny cells needed to make a baby. Sperm production normally continues through adult life. Sperm mix with other fluids to make semen, a white, sticky fluid.

When semen leaves through the penis, that is ejaculation. The cells, the fluid and its release have different names:

Erections and wet dreams

An erection happens when extra blood fills the penis and makes it stiff. Erections can happen on their own during puberty. They go away by themselves.

A wet dream, or nocturnal emission, is ejaculation during sleep. For example, someone may wake with semen on their pajamas. Semen is different from urine, so this is not wetting the bed. Some people have wet dreams and some do not. Either is normal.

Some boys also get swelling or tenderness around the nipples. This is common and usually goes away within one to two years.

Learn about other bodies too

Everyone benefits from understanding periods and wet dreams. If a classmate needs help, you can respond kindly. Keep questions about another person's body private, and avoid jokes about their voice, hair or growth.

A period, or menstruation, is blood and tissue from the uterus lining leaving through the vagina. It is a normal body process. The blood does not come from an injury.

What happens during the cycle?

The uterus grows a thicker lining, ready in case a pregnancy starts. An ovary usually releases an egg during the cycle. In early cycles, periods can happen without an egg being released.

If no pregnancy starts, the thick lining breaks down and leaves as a period. A new lining then grows. This repeating pattern is the menstrual cycle.

A period usually lasts 2–7 days, often about five. Flow is usually heaviest in the first two days. Total blood loss is about 20–90 milliliters, roughly 1⅓–6 tablespoons, across the whole period.

Count from one start to the next

Day 1 is the first day of bleeding. The cycle ends the day before the next period. The next starting date is day 1 of a new cycle.

Periods begin on April 2, April 30 and June 1:

1. April 2 to April 30 is 28 days. The first cycle ends April 29.
2. April 30 to June 1 is 32 days. The next cycle ends May 31.

Count all the days in the cycle, including days without bleeding. A five-day period is not a five-day cycle.

Adult cycles usually last 21–35 days. Young people's cycles commonly last about 21–45 days. In the first year or two, the gaps often vary.

Use dates as a guide

Mark each first day on a calendar. If a period starts March 3 and cycles are about 28 days, adding 28 days gives March 31 as an estimated next start. A five-day period beginning March 3 would last through March 7.

A prediction helps you pack supplies. It cannot tell you the exact date, especially when cycles are still changing.

Care and help on period days

Cramps are aches in the lower belly or back. A warm heating pad, rest, water and gentle movement can help. Use pain medicine only with a parent's or doctor's okay. You can shower, swim with a suitable product and take part in sports during a period.

Tell a trusted adult and ask for medical help if bleeding lasts over seven days, soaks a pad or tampon every hour or two, or pain stops normal activities. Ask too if there are more than 90 days between periods, even once.

Period products absorb or collect the flow. You can choose what feels comfortable and learn how to use it. Many people start with pads.

Four main products

A thin panty liner can help with discharge or very light flow. Reusable cloth pads can be washed and used again.

Change a pad about every 3–4 hours during the day, sooner if full or damp. Choose a size that suits the flow, including a night pad when needed.

For tampons, use the lowest absorbency that handles the flow. Change every 4–8 hours and never leave one in over eight hours. This helps reduce the risk of toxic shock syndrome, a rare but serious illness. Sudden fever, vomiting, faintness or a sunburn-like rash during tampon use means remove it, tell an adult and get medical help immediately.

Empty, rinse and clean a cup as its package directs. Rinse used period underwear in cold water, then wash it. Different products have different care instructions.

Plan changes during the day

Suppose you put on a pad at 7:30 a.m. You could plan a change at 11:00 a.m., then 2:30 p.m. Each gap is three and a half hours. If the pad feels full earlier, change earlier.

Wash your hands before and after changing products. Wrap used pads or tampons and put them in a trash can. Flushing them can block pipes.

Be ready away from home

Pack a small bag with two or three pads or other products, spare underwear and a bag for used clothes. You can keep it in your backpack before your first period.

If a period starts unexpectedly, ask a teacher or school nurse for a product. Folded toilet paper can help briefly until you get one. First periods can be light and look brown.

If blood leaks onto clothes, ask for help and change when you can. A sweater tied around your waist can cover a mark. Rinse the stain in cold water later.

Personal hygiene means keeping your body clean and healthy. Puberty brings more sweat and oil, so your routine may need to change.

Wash skin and change clothes

Shower or bathe daily or most days, and after sweaty activity. Use soap and water on your underarms, groin and feet. Put on clean underwear and socks each day. Wash sports clothes after each use.

Deodorant reduces or covers body odor. Antiperspirant reduces sweat; some products do both. Apply it to clean, dry underarms. Washing still matters because scent does not remove sweat and bacteria.

After basketball, Theo showers but puts on the same sweaty shirt. The shirt can still smell because sweat remains in the fabric. Changing the shirt is part of getting clean, too.

Care gently for skin and hair

Wash your face gently twice a day and after sweating. Use warm water and a mild cleanser. Avoid squeezing or picking pimples, which can leave marks or scars. Ask a doctor or pharmacist about acne that hurts or bothers you.

Hair may get oily faster in puberty. Wash it as often as it needs, which might be daily or every other day. Hair types differ, so find a routine that works for yours.

Wash private parts safely

Wash the outside of the genitals each day with warm water. A mild, unscented soap is optional. The vagina cleans itself: do not wash inside it or use perfumed sprays there.

If you have a foreskin, pull it back gently only as far as it moves easily. Rinse underneath and slide it back into place. Never force it.

Shaving is a personal choice. If you choose to shave, ask a trusted adult to show you how. Use your own clean razor and do not share it.

Fit care into your day

A routine makes jobs easier to remember. For example:

• Morning: wash your face, use deodorant if wanted, put on clean underwear and socks, and brush your teeth.
• After a sweaty activity: wash, change clothes and put used sportswear in the laundry.
• Evening: gently wash your face and brush your teeth.

Keep the things you use where you can find them. If you are running out of soap, clean socks or period products, tell a caregiver before you need them.

A growing body needs rest, food, water and movement. These habits also help you focus, handle stress and enjoy your day.

Give sleep enough time

Children aged 6–12 need about 9–12 hours of sleep each night. Teenagers aged 13–18 need about 8–10 hours. During sleep, the body grows and repairs itself.

You may begin feeling sleepy later in the evening. Your morning alarm might still stay the same. Work backward from waking time to find a bedtime that leaves enough sleep.

For a 6:45 a.m. wake-up and ten hours of sleep:

1. Count back six hours and 45 minutes to midnight.
2. Count back the remaining three hours and 15 minutes.
3. That gives 8:45 p.m. for lights out.

For nine hours, lights out would be 9:45 p.m. Allow time before that to get ready and settle down. Keep sleep and wake times steady, including on weekends. Turning screens off about an hour before bed can help your brain settle.

Eat and drink through the day

Have regular meals with different kinds of food. Fruit, vegetables, whole grains and protein foods all support growth. Protein foods include beans, eggs, fish and meat. Milk, yogurt and fortified alternatives supply calcium for bones. Iron-rich foods help replace iron lost during periods.

For example, a meal could include rice, beans, vegetables and yogurt or a fortified alternative. No single food does every job. Drink water through the day, especially in hot weather and during activity.

Feeling hungrier during a growth spurt is normal. Skipping meals to avoid puberty weight gain can leave you tired and make it hard to focus.

Move each day

Aim for at least 60 minutes of physical activity daily. You can build that time from several activities. Brisk walking, biking, dancing and active games all offer ways to move.

Movement helps build strong bones and muscles. It can also improve sleep and lift your mood. Choose activities you enjoy so they fit naturally into your day.

Puberty can bring stronger emotions and quicker changes in mood. You might feel cheerful, then suddenly grumpy or embarrassed. These mood swings are common as the brain develops and the body changes.

Tiredness, hunger and stress can make feelings stronger. You may also want more privacy or worry more about fitting in.

Pause before choosing a response

Naming a feeling can help you decide what to do. Try “I feel worried,” “I feel embarrassed” or “I feel angry.” Then take a short break and breathe slowly and comfortably. A walk, calming activity, written note or conversation can help too.

Jordan's voice cracks during a class answer. A friend laughs, and Jordan wants to shout back.

1. Jordan names the feeling: “I feel embarrassed and annoyed.”
2. Jordan pauses and takes a few calm breaths.
3. Jordan remembers that a growing voice box can cause cracks.
4. When calmer, Jordan says, “Please stop joking about my voice.”

If the teasing continues, Jordan tells a teacher. Calming down helps Jordan speak clearly; it does not make the teasing okay.

Feelings about people and appearance

A crush is a special feeling of liking someone. Some people have crushes at your age and some do not. Having a feeling does not mean you have to do anything about it.

Body image means how you think and feel about your body. Comparing your changing body with someone else's can make you worry. People grow at different times. Ads and online photos may also be edited or filtered, changing skin, shape or other features.

For example, a photo showing perfectly smooth skin may hide spots with a filter. It is an unfair measure of how skin should look. Your body also helps you move, learn, rest and enjoy things, beyond how it looks.

When feelings need more support

Tell a trusted adult if sadness, worry or anger lasts for weeks, feels too big to handle, or stops you sleeping, eating or enjoying things. You can ask for help before you know exactly what to call the feeling.

Growing up can change friendships and family life. You may gain new interests or want more choices. Good relationships leave room for those changes and for your feelings.

Respect and pressure from friends

Good friends respect your choices. Peer pressure means people your age push you to do something. You might hear, “Everyone is making the joke, so you should too.” You can say no, change the subject or walk away.

Bodies, voices, pimples and periods are not reasons to tease someone. Keep private information private. If a friend tells you about a first period, you can offer help without telling the rest of the class.

More independence at home

Wanting privacy is common. Talk calmly with caregivers about what would help. Listen to their concerns and agree on a rule, such as knocking before entering a bedroom.

More independence comes with more responsibility. You might organize your school bag, manage your washing routine or help more at home. Taking charge of these jobs can build trust. You still have people to turn to when you need support.

Check information before believing it

A trusted adult listens, helps keep you safe and gives reliable answers. That could be a caregiver, relative, teacher, school nurse, counselor or doctor.

For health questions, use people with health knowledge and websites run by children's hospitals or government health services. Rumors, jokes and ads can spread false ideas. A video being popular does not make its advice accurate.

Sam hears, “Shaving makes hair grow back thicker.” Sam asks a school nurse and checks a children's hospital website. Shaving leaves a blunt tip that can feel coarser. It does not change the hair's thickness. Checking the explanation helps Sam understand why the rumor sounds believable.

Start a conversation

You can say, “Can I ask you something about growing up?” If speaking feels awkward, write the question down. Talking during a walk or another shared activity can feel easier. Choose someone who listens and helps you find a clear answer.