The intermediate mesoderm is located between the somite and the lateral plate mesoderm. It will contribute to the development of genitourinary structures such as the gonads, reproductive ducts, kidneys and ureters.
During the third and fourth weeks of development, cells that migrate from the epiblast region into the primitive streak contribute to the formation of the mesoderm. This process is gastrulation. Midline mesodermal cells form the notochord. Lateral to the notochord, the mesoderm is the paraxial mesoderm which will form clumps of tissue called somites. Somites are usually visible on the surface of the embryo.
Lateral to the paraxial mesoderm is the intermediate mesoderm which will form genitourinary structures. The lateral plate mesoderm splits into two layers to form the linings of the body cavities and the coverings of the visceral organs.
In the view to the right, we are looking down on the surface of the trilaminar embryonic disc to see the various regions of mesoderm through the surface ectoderm.
Below is a cross section of an embryo.