This document discusses the role of stem cells in animal reproduction. It defines stem cells as non-specialized cells that can proliferate and renew themselves through cell division, and differentiate into specialized cell types. It describes the different types of stem cells - totipotent, pluripotent, multipotent and unipotent. It discusses sources of stem cells including embryonic stem cells, induced pluripotent stem cells, fetal stem cells and adult stem cells. It summarizes potential applications of stem cells in regenerative medicine and their use in endometrial repair, vaginal reconstruction, erectile dysfunction, and in-vitro gamete production.