It is now possible to culture cells from most organs of the body under conditions in which they continue to express at least some of their differentiated traits, and to model some of the differentiation processes that occur during embryonic and adult life. How much can these cultures tell us about the acquisition and maintenance of the differentiated state? To answer this question I shall outline the features of several cell culture models, dividing them into categories according to whether they mimic differentiation during development, differentiation of adult stem cell progeny, or the transition from one differentiated phenotype to another. In spite of the diversity of cell types under consideration, it is possible to detect some common themes: the stability of the differentiated state; the relationship between proliferation and differentiation; the relative importance of intrinsic cellular programming and environmental regulation; and possible mechanisms for transcriptional control of the genes that are activated during differentiation. In recent years cell culture models have yielded a great deal of information about differentiation and the way is now clear for even more exciting discoveries.