The basis of growth and development of all biological systems is cellular growth, cell division, and cell differentiation. Using cell and tissue culture opens up possibilities to investigate influences of nutrients and growth regulators on each of these phenomena, without confounding effects of remote tissue, as would be the case when using intact plants. Such studies should help to understand influences of these factors on cell life in more details. On the other hand, the use of cell cultures for specific aims, like the cloning of plants, production of secondary metabolites, gene technology, or plant breeding, requires a thorough understanding of these phenomena to optimize such procedures. Still, the interpretation of results of many such experiments remains mainly empirical, because of the lack of detailed knowledge of these systems. Attempts to integrate the results of histological, biochemical, and cytological assessments for interpretation of a given system are still quite rare.