Of the three, the opossum is most closely related to the kangaroo. Didelphis means having two wombs. After mating, a female opossum will give birth in 13 to 14 days, one of the shortest gestation periods of any mammal. A newborn opossum is about the size of a honeybee. Incredibly small, an entire litter of newborn opossums can fit in a standard tablespoon.
Newborn opossums arrive in their mother's pouch by crawling there on their own.
Though tiny and blind, newborn opossums instinctively climb upward towards their mother's pouch where they will each fasten to a teat and remain there for about 3 months. A full-grown opossum is about the size of a house cat. The adult opossum frequently uses its tail to assist in climbing. Opossums eat practically anything. Most opossums live in underground dens.