The first event of neurilation is the formation of a thickened area of cells, called the neural plate. The neural plate forms at the cranial end of the embryo and grows in a cranial to caudal direction. The cranial or head end of the neural plate indicates the region of the future brain, and the narrower caudal or tail end represents the future region of the spinal cord.
By the end of the third week of development, the lateral edges of the neural plate become elevated and move together to form the neural folds. The resulting space created by the folding of the neural plate is called the neural groove. The neural folds fuse together and the neural plate transforms into the neural tube, the precursor to the central nervous system. Fusion of the neural tube usually begins in the middle of the embryo, extending in both cranial and caudal directions.
During the closure of the neural tube, cells on the crest of the neural folds detach, forming a new cell population, called the neural crest. These cells contribute to the formation of the peripheral nervous system. Once the neural tube has completely fused, The process of neurilation is complete.