On the surface, Coy Mathis is a typical seven-year-old girl.
She likes dressing up, gravitates towards the colour pink, and enjoys playing with her dolls... but Coy was born a boy.
Jeannette Francis investigates the complex and fascinating world of transgender children.
Backed by medical experts, a growing number of parents in the United States are allowing their kids to live openly as the other gender.
For the children involved, the switch can end years of unhappiness and feelings of being trapped in the wrong body.
But like other members of the transgender community, they can face deep social stigma and discrimination.
So how young is too young to change sex?
See Jeannette's insight into the life of Crossover Kids above.
SBS's Insight program also discussed the issues surrounding transgender children in September 2013. Watch the show.