A node, or primitive knot, is an enlarged group of cells located in the anterior portion of the primitive streak in a developing gastrula. The node is the site where gastrulation, the formation of the three germ layers, first begins.

Gastrulation is an early stage in embryo development in which the blastula reorganizes into the three germ layers: the ectoderm, the mesoderm, and the endoderm

August Antonius Rauber was an embryologist and anatomist who examined gastrulation in avian embryos.

Embryonic images displayed in Life magazine during the mid-twentieth century serve as a representation of technological advances and the growing public interest in the stages of embryological development.

Nicole Marthe Le Douarin was one of the first progressive female pioneers of developmental and embryological research.

“A Diffusible Agent of Mouse Sarcoma, Producing Hyperplasia of Sympathetic Ganglia and Hyperneurotization of Viscera in the Chick Embryo,” by