Studies have proven that both human and bovine breast milk contain naturally occurring cannabinoids, further supporting the importance of the Endocannabinoid System, or “ECS” - but this is only a small piece of a greater picture. Cannabinoids and cannabinoid receptors are present in abundance in the human body - in our brains, lungs, digestive system, connective tissues, hormone-producing glands, skin, hair, bones, and immune system - and are even involved at the very, very beginning of a human body, as CB1 and CB2 cannabinoid receptors are present during the process of implantation of an embryo. The relationship between cannabinoids and their receptors with respect to embryos and the uterus still has a lot of questions unanswered, but at a certain point during the reproductive cycle, the uterus contains the most cannabinoids of any mammalian organ, and the embryo itself is laden with cannabinoid receptors. This heavily suggests the role of cannabinoids in properly timing development and growth of the embryo with the development of the uterine lining, potentially affecting the likelihood of successful implantation. The specific cannabinoid present in the uterus, anandamide, has been proven to affect embryonic growth - it halted development when added to embryos, but when the addition of anandamide was stopped, the embryos resumed normal development. These findings reach far implications in both directions - both with our understanding and treatment of infertility, and the possibility of a new form of contraception.