Embryonic development is the process by which the fertilized egg, a single apparently amorphous cell, develops into the final adult form composed of many cells arranged in structures with specific shapes. It does not consist simply of the growth in size of a preformed 'homunculus' but is tremendously dynamic, characterised by large scale cell movement and tissue remodelling. This process has to be carefully choreographed so that morphogenesis takes place correctly and reproducibly.
Cell movements play a central role throughout mammalian embryogenesis, for instance during gastrulation, in the formation of the germ cell lineage and during the formation of the heart. An understanding of such dynamic processes is important in integrating our increasingly detailed knowledge of molecular and genetic regulatory networks into the context of cellular interactions during embryogenesis. The movement of cells during development is also intimately connected to their ultimate fate. Knowing the normal fate of cells is important not only for an understanding of development, but also has implications for therapy in humans, as it relates to the developmental potential of embryonic cells that may represent populations of stem cells.