They are called ' The Guevedoces' or ' The M achihembras', which roughly translates to 'Penis at 12' and 'first a woman, then a man'. A BBC documentary called Countdown to Life: The Extraordinary Making of You explored the rare condition of these children from a small village in the Dominican Republic.

One in every 50 children here appear to be a girl, but develop testicles, penis and muscles once they hit puberty.

Source: BBC

Before Johnny became a male, he was a girl who was known as Felicita. He was brought up as a girl and remembers going to school in a little red dress. When he was young, he'd play with other girls, but after the age of seven he started to change.

“I did not feel good, I no longer liked to wear a skirt, and I was no longer drawn to play with girls. All I wanted to do is play with toy guns and boys”, he said.

Source: elegraph

Johnny is hopeful about his future and says," I'd like to get married and have children, a partner who will stand by me through good and bad."

It goes without saying that something like sex change after 12 years brings not only physical but also huge psychological changes. The identity crisis that comes with it is visible from the fact that some boys live as men, but some go through an operation to live life as a woman.

Confused? Here is the scientific reason behind this transformation that some of these children go through.

A normally conceived female has XX chromosomes and a male has XY chromosomes. For the initial few weeks of life in the womb, they don't have any sex but they start developing nipples.

After 8 weeks in the womb, a baby starts developing organs, which classify them as a male or a female. The male Y chromosome instructs the gonads to become testicles and the testosterone is converted into a hormone called dihydro-testosterone, which is responsible for the formation of a penis. A female does not make dihydro-testosterone which makes the tubercle a clitoris.

The kids in this village don't have male genitalia because they are born with a genetic deficiency of 5-alpha Reductase, which makes the boys seem like a girl.

At puberty, however, they face a rush of testosterone and this time the body does respond, which makes them sprout muscles, testes and a penis.

These village children are an important case-study for researchers all over the world. In fact, Dr Imperato’s research on these children was picked up by an American pharmaceutical company called Merck, which used it to create a drug called Finasteride. The drug is a blessing to men because it blocks the action of 5-α-reductase, which is used to treat mild enlargement of the prostate and male pattern baldness.