"A kangaroo mother can have three joeys simultaneously at different stages of development: an embryo in her womb (kangaroos can do what’s called embryonic diapause which means sort of putting the development on pause until she’s ready for it to develop further), a joey in her pouch attached to one nipple, and a joey out of the pouch on the ground who nurses from the other one. The amazing thing? Each of her nipples make different formulations of milk for each joey’s different nutritional needs."