In organ cultures, whole embryonic organs or small tissue fragments are cultured in vitro in such a manner that they retain their tissue architecture. In contrast, cell cultures are obtained either by enzymatic or mechanical dispersal of tissues into individual cells or by spontaneous migration of cells from explants; they are maintained as attached monolayers or as cell suspensions.

Freshly isolated cell cultures are called primary cultures; they are usually heterogeneous and slow growing, but are more representative of the tissue of their origin both in cell type and properties. Once a primary culture is subcultured, it gives rise to cell lines, which may either die after several subcultures (such cell lines are known as finite cell lines) or may continue to grow indefinitely (these are called continuous cell lines).