Mother kangaroos sport a pouch on their belly, made by a fold in the skin, to cradle baby kangaroos called joeys. Newborn joeys are just one inch long (2.5 centimeters) at birth, or about the size of a grape. After birth, joeys travel, unassisted, through their mom’s thick fur to the comfort and safety of the pouch. A newborn joey can’t suckle or swallow, so the kangaroo mom uses her muscles to pump milk down its throat. At around 4 months, the joey emerges from the pouch for short trips and to graze on grass and small shrubs. At 10 months, the joey is mature enough to leave the pouch for good.

–National Geographic Kids