This monograph intends to introduce the postnatal development of morphological features relevant to the reader interested in the neurobiology and pathology of the hippocampal formation in the complex phenomena underlying the progressive anatomical and functional maturation of this brain region. This review is focused in the morphological aspects, while more detailed basic phenomena of neuronal maturation, no doubt, of great interest, will be only marginally referred to, although a selection of behavioral and clinical aspects will be briefly addressed too as an attempt to illustrate real situations in different clinical specialties.