Morula

A stage in the development of the embryo prior to the blastula in which a cluster of complex cells form from the solid mass of blastomere cells after the zygote splits or cleaves, resulting in 12-15 cells and looking like a mulberry (hence its name; see figure below).  Human embryos implant at this stage in the uterine wall.  This stage is followed by the formation of a cavity in the cellular mass (the blastoceol which indicates the formation of the blastocyst).   

Morula at four days after conception, which resembles a mulberry fruit. 

See Blastocyst, Blastomere, Blastula, Embryo