A host cell is a living cell that accepts or takes in another organism, usually one much smaller than itself, and provides it with nutrients and an environment in which it can grow and reproduce. This process is known as endocytosis or phagocytosis. The host cell surrounds the foreign particle and brings it into its interior where it can be broken down and utilized by the host cell for energy or other purposes. In biology, this term often refers to a bacterial or yeast cell that has been taken over by a virus in order to reproduce itself.