The tissue of the central nervous system is made up of two classes of cells that may be broadly categorized as neurons and glia. Neurons are anatomic, functional, and trophic units of the brain. Despite great variability in size and shape, all neurons share common morphologic features, which are those of the key elements of a highly complex communication network. The neurons are the dynamically polarized cells that serve as the major signalling unit of the nervous system. The hippocampal neurons play a special role in learning and memory and cultured hippocampal neurons are a useful model for studying neuronal phenomena such as differentiation, survival, process growth, and synapto-genesis.