How does the joey develop from birth to adulthood?

The joey (a baby kangaroo) spends the majority of its developing childhood in its mother’s pouch in order to stay warm, safe, and have easy access to milk.
The joey is usually about the size of a jellybean at birth (approximately two grams). Immediately after birth, the pink and hairless joey climbs up the mother kangaroo’s fur and into her pouch. The first several months of the joey’s development simply involve nursing, sleeping inside the pouch, and growing a thin layer of fur. After this “incubation” period, the joey opens its eyes, starts to observe its surroundings, and eats small amounts of grass in order to supplement its milk. After about 8 months, the joey finally emerges from the pouch. The joey plays and explores to develop its muscles, returning to the pouch to rest and feed. At the 10 month mark, the joey is typically too large to return to the mother’s pouch and is no longer reliant on her milk for survival. Even though the joey is still not fully grown, this separation from its mother marks the transition into adulthood.