Somite

The somites are derived from the mesoderm and are embryonic structures located on either side of the neural tube and which form the future body's central nervous system.

The somites subdivide during embryonic development into sclerotomes and dermatomyotomes which in turn sub-divide into dermatomes and myotomes.

Dorsal view of an embryo. The somites, shown in red, are aligned along the neural tube. © Gray's Anatomy, Wikimedia public domain