How are cows able to eat and digest plant matter that contains cellulose?

Tiny microbes and protozoa live in the animal's stomach that help digest this matter and enable the cow to get the nutrients from this material. Also, a multi-chambered stomach allows a ruminant like a cow to add multiple steps to allow for more thorough digestion of such plant material that a monogastric animal, like a human or a pig, would not be able to digest.