Human reproduction is the most dynamic of processes. The events which lead to the birth of a normal healthy infant have their origin long before actual fertilization. Indeed, the whole process can be looked upon as a continuum. Human fertilization and early development, once sequestered in the protective environment of the fallopian tubes and uterus, have now been exposed in the laboratory. These events have, over time, been extensively observed and catalogued in animal models. The tools of modem morphology and molecular biology have reopened issues long since considered settled as facets of...