Twins
are the set of two offspring produced in the same pregnancy. They can be monozygotic
or dizygotic. Monozygotic twins are produced from the same zygote, that is, a
single zygote divides to give rise to two embryos. They are usually
identical. Dizygotic twins are formed when a female releases two eggs that are
fertilized by two different sperms and result in the formation of two zygotes,
and eventually two embryos.