Like many other mammals, mice reproduce by mating with one another by using their sexual reproductive organs. Mice are polygamous, which means that male mice often mate with several different females. Breeding between mice occurs all throughout the year and commonly results in female mice giving birth to around five or six young per litter.
After being pregnant for 19 to 21 days, females give birth to tiny young that are helpless, blind, without fur and weigh only 1 gram. Baby mice grow fur after 10 ten days, and they are finally able to open their eyes after a period of about 2 weeks. After 3 weeks, young mice are mature enough to leave their mother's nest and explore new territory.