Mouse intestines are very much like those of other vertebrate animals. The large intestine is wider and shorter than the small intestine and its primary function is to absorb water and electrolytes from digestive residues and store fecal matter.

The word "mouse" has no meaning in scientific classification, but species of many families of small rat-like rodents are commonly referred to as mice. Most mouse species, such as the common house mouse, belong to the family Muridae. The other major mouse families are Cricetidae (grasshopper mice, harvest mice), Heteromyidae (pocket mice), and Zapodidae (jumping mice and birch mice).

Mice occur in nearly every habitat and every continent but Antarctica, either naturally or through introduction by humans. Their diet consists of grains, roots, fruits, insects, grass, and "people food". The brownish-gray house mouse originated on the Eurasian continent but gained a worldwide distribution thanks to human dispersal and travel. These mice can multiply quickly, usually breeding every 10-17 weeks a year and producing 5 to 10 young per litter.

Laboratory mice are special breeds of house mice and are used in many scientific experiments because of their close mammalian relationship to humans. Compared to larger mammals, mice and other rodents are small, easy to handle, inexpensive to house, and breed quickly. During the late 20th Century (and on into the current century), scientists bred different strains of mice with genetic deficiencies in order to produce models for human diseases.