During telophase, a partition or cell plate divides the cytoplasm rather than a cleavage furrow. At this stage, each cell is unspecialized and can potentially develop into a separate organism. A human embryo is in the morula stage as it travels down the fallopian tube. The individual units are one-seeded drupelets rather than cells. The undifferentiated cells of a human blastocyst are called stem cells.
Stem cells give rise to various tissues and organs in the body.
Embryonic stem cells are especially remarkable because they can literally give rise to a complete organism composed of tissues and organ systems. Through complex gene interactions, these cells can literally develop into any number of cell types found in the human body. The controvesy over the use of embryonic stem cells in research involves the question of what consitutes a human being. With the sophisticated techniques of modern biotechnology, the nucleus of any undifferentiated cell has the potential to grow into a clone if it is placed in a denucleated egg cell. The bottom line here is that the cells must be placed in a carefully controlled environment in order to grow.