Professor James M. Tanner, a child development expert, was the first to identify the visible stages of puberty.

Today, these stages are known as the Tanner stages, or more appropriately, sexual maturity ratings (SMRs). They serve as a general guide to physical development, although each person has a different puberty timetable.

Females: Typically starts after 8th birthday

Males: Typically starts after 9th or 10th birthday

Both females and males:

• The brain begins signaling the body to prepare for changes

• The hypothalamus starts to send gonadotropin-releasing hormone (GnRH) to the pituitary gland

• The pituitary gland begins making luteinizing hormone (LH) and follicle-stimulating hormone (FSH)

• There are no noticeable changes during stage 1

Females: Typically starts between ages 9 and 11

• Breast buds start to form under the nipple. They may be tender and grow at a different rate - that’s normal.

• The areola (the darker area surrounding the nipple) expands.

• The uterus grows larger

• Pubic hair begins growing on the lips of the vulva

Males: Typically starts around age 11

• The testicles and scrotum grow larger.

• Pubic hair starts to grow on the base of the penis.

Females: Typically starts after 12th birthday

• A major height growth spurt begins (averaging around 3.2 inches annually).

• Breast buds continue to grow.

• Pubic hair becomes thicker.

• Hair begins forming under the armpits.

• Acne may start to appear on the face and back.

• Fat begins to accumulate on the hips and thighs.

Males: Typically starts after 13th birthday

• Height growth increases 2-3.2 inches per year.

• The penis becomes longer, and the testicles continue to grow larger

• Some breast tissue may begin forming under the nipples. This happens to some males during development but usually disappears within a few years.

• Males begin to have nighttime ejaculations, also known as wet dreams.

• The voice changes and may “crack” between higher and lower registers.

• The muscles expand.

Females: Typically starts after the 13th birthday

• The breasts become fuller.

• Many females get their first period, although it can happen earlier

• Height growth slows back down to 2-3 inches per year.

• Pubic hair continues to grow thicker.

Males: Typically starts after the 14th birthday

• The testicles, penis, and scrotum grow more prominent and darker in color.

• Hair begins to form under the armpits

• The voice deepens permanently

• Acne may start to develop

Females: Typically starts after the 15th birthday

• Final adult height is reached between one and two years after the first period.

• The breasts reach their approximate adult size (although breasts can continue to develop through age 18)

• Periods start to become regular, usually lasting six months to two years.

• Pubic hair reaches the inner thighs.

• The genitals and reproductive organs are fully developed.

• The hips, thighs, and buttocks fill out in shape.

Males: Typically starts after the 15th birthday

• Growth in height slows, but muscle growth may continue.

• Final adult height is typically reached

• The penis, testicles, and scrotum reach their final adult size

• Pubic hair spreads to inner thighs

• Facial hair begins to grow.

Your body goes through many phases. Like puberty, you can’t stop some of these changes from occurring. Also, like puberty in adolescence, these stages are highly tied to hormone production.

What do these additional phases of hormonal body changes look like?

Females: As a young woman, your body continues to grow and mature. You typically reach your peak physical ability during this time.

Physical changes include:

• Maximum bone mass. Your body reaches its peak bone mass in your 20s.

• Maximum muscle strength. Like males, your muscles are strongest during this time.

• Regular periods. Your estrogen levels peak in your mid or late 20s, causing predictable periods.

Males: During this time, you continue to mature as you physically transition out of your teenage years. This includes physical changes like:

• Maximum bone mass. You achieve your peak bone mass, the most bone tissue you’ll have.

• Maximum muscle mass. Your muscle also reaches its peak mass and strength.

• Slowing prostate growth. During puberty, your prostate grows quickly. But at age 20, it starts to grow very slowly.

Females: Second puberty in your 30s refers to perimenopause or the transition into menopause. It can start in your mid- or late 30s.

Irregular estrogen levels cause the physical changes of perimenopause. These changes include:

• Declining bone mass. Your body mass begins to decrease.

• Declining muscle mass. You’ll also start to lose muscle mass.

• Changing skin. As your skin loses elasticity, you may develop wrinkles and sagging skin.

• Graying hair. Some of your hair might turn gray.

• Irregular periods. By your late 30s, your periods become less regular. Your fertility also decreases.

• Vaginal dryness. The lining of your vagina becomes drier and thinner.

• Hot flashes. A hot flash, or an abrupt feeling of heat, is a common sign of perimenopause.

Males: By your mid-30s, testosterone levels gradually decrease for the average man. 

The physical changes you experience are usually associated with aging in general. These may include:

• Declining bone mass. Your bone mass slowly decreases in your mid or late 30s

• Declining muscle mass. You begin to lose muscle mass.

• Changing skin. You may develop wrinkles or age spots in your late 30s

• Graying hair. After your mid-30s, you’re more likely to develop gray hair.

Females: In your early 40s, the physical changes from the previous decade continue.

But by your late 40s, your body will start to enter menopause. Some people call this transition a second puberty. 

Menopause causes changes like:

• More rapid bone loss. Once you reach menopause, you’ll lose bone more quickly.

• Decreasing height. Like men, women lose height as the discs between their vertebrae get smaller.

• Weight gain. Your body changes how it uses energy, making you more prone to weight gain.

• Irregular or no periods. As your body makes less estrogen, your periods become even more irregular. Your periods will likely stop by your early 50s.

Males: The changes that occur in your 30s continue into your 40s.

At the same time, physical changes due to decreasing testosterone will become more noticeable. These changes are known as male menopause or andropause.

You can expect:

• Fat redistribution. Fat may accumulate in your belly or chest.

• Declining height. In your spine, the discs between your vertebrae begin to shrink. You may lose 1 to 2 inches in height.

• Growing prostate. Your prostate goes through another growth spurt. This might make it difficult to urinate.

• Erectile dysfunction. As testosterone decreases, it becomes more difficult to maintain an erection.