Twins that appear quite alike are usually referred to as "identical" twins. However, the more accurate term is "monozygotic". Monozygotic twins share nearly the same genes, but they are not completely identical.
How are monozygotic twins formed?
This type of twin begins when a sperm fertilizes a single egg, and when a fertilized egg (called a fertilized egg) moves into the uterus, cells divide and grow into a blastocyst. In monozygotic twins, the blastocyst divides and develops into two fetuses.
Simply put, monozygotic twins occur when one fertilized egg splits into two. From there, two fetuses grow into two children. Monozygotic (“mono” meaning one and “zygote” meaning zygote) is the term used to describe this process.