Find out everything you've always wanted to know about identical twins – from how they form to what makes them unique.

Fraternal twins come from two separate fertilized eggs that develop in the womb at the same time, each with their own placenta and amniotic sac. Like any siblings, they may – or may not ...

The chorion lies closest to the placenta. The chorionic sac encompasses the fetus and the amnion and is covered with chorionic villi until the 8th week. After the 8th week, these villi are ...