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

It makes sense that identical twins would have the exact same DNA, right? Spoiler alert: Not always! Here's why. Identical ...

The mature egg can then be fertilized by a sperm cell, which creates a zygote — a fertilized egg cell. After fertilization, the zygote needs to successfully implant into the uterine lining ...

Identical twins arise from a single fertilized egg, or zygote, splitting into embryos with duplicate DNA, but what causes the split remains unknown. Zygote splitting was once thought ...