Mammals and vertebrates come from a single cell via the fertilization of an oocyte with a sperm cell. This single cell gives rise to all of the specialized cells comprising the adult body. Genetic, as well as epigenetic, factors play an important role in early human development. Yet, the mechanisms governing early development are less well understood in humans than in some other species such as flies or mice. In the quest to advance our knowledge of our own development, we are building a complete genetic map (transcriptome) of the early embryo from day 1 (post fertilization) to day 12 of development using microarray, qRT-PCR, immunohistochemistry, in situ hybridization and other molecular techniques. This may lead to a better understanding of the causes of human infertility as well as a variety of human inherited diseases.