Identical twins are siblings who develop from a single fertilized egg that splits into two embryos. This means they share the same genetic material, making them genetically identical. They often look very similar, with the same hair color, eye color, and facial features. However, they can still have differences in personality and preferences due to environmental factors. Identical twins are also known as monozygotic twins. They typically share the same placenta during pregnancy, which can lead to unique health considerations. Studies on identical twins help scientists understand the influence of genetics versus environment in areas like behavior, intelligence, and health.