The use of cellular models is crucial for the further advancement of nutritional science. This chapter describes cellular models in ex vivo and in vitro experimental systems. In vivo studies are those carried out using the whole animal, and intervention studies. Ex vivo experiments are done using living tissue, but in a laboratory apparatus outside the organism where natural conditions are maintained as far as possible. Cultured cell models can be divided into two general types, primary cells and immortalised cell lines. For culture in vitro, most primary cells must first be released from the extracellular matrix with no, or minimal, damage to the plasma membrane, as otherwise they will not be able to survive. The techniques used for cell culture are similar for both primary cells and immortalised cell lines. Methods for cell culture and live cell imaging are improving all the time and becoming more and more sophisticated.