Epithelial cells are one of the two main types of cells found in the body; the other main type being mesenchymal cells. Epithelial cells exist in sheets of cells that are tightly joined together by adhesion molecules; therefore, these epithelial cells are immobile, while the mesenchymal cells exist as independent cells and are highly motile. Many organs, including breast and lungs, are mostly made up of epithelial cells. When these epithelial cells become cancerous, they are initially confined to the organ in which it originated due to the continued expression of the adhesion molecules. However, eventually these adhesions may break thereby allowing the epithelial cancer cells to become detached and more motile, which facilitates the spread of the cancer cells to other regions of the body. We and others have found that the breaking of the cell-cell adhesion within carcinomas is facilitated by a process known as epithelial-mesenchymal transition (EMT), as a result these carcinoma cells appear similar to mesenchymal cells in shape and behavior. Therefore, this acquisition of mesenchymal traits through EMT seems to facilitate the spread of cancer to other organs. The EMT process is a reminiscent of embryo development. It is this deadly spread of cancer, (metastasis) mediated by EMT, that causes the majority of cancer-related mortalities.