Color enhanced LM of human ovum, 8-cell stage. The eight-cell stage is a period in embryonic development when the conceptus has undergone three cleavages from a single cell, resulting in eight cells. The egg cell, or ovum, is the female reproductive cell (gamete) in oogamous organisms. In all mammals the ovum is fertilized inside the female body. The human ova grow from primitive germ cells that are embedded in the substance of the ovaries. Each of them divides repeatedly to give secretions of the uterine glands, ultimately forming a blastocyst. The ovum is one of the largest cells in the human body, typically visible to the naked eye without the aid of a microscope or other magnification device. When egg and sperm fuse, a diploid cell (zygote) is formed, which rapidly grows into a new organism. Magnification: 1000x at 35mm.