 The article discusses the processes of abstract EMT and MET, which are integral to normal development and cancer metastasis, and reviews the molecular pathways that contribute to them. It compares embryogenesis and development with cancer metastasis, discusses signaling pathways and receptor expression in both tumor and stromal cells, and explores clinical implications and epigenetic events that regulate EMT-MET processes. The hypothesis is that reversible epigenetic events regulate both EMT and MET, and thus, also regulate the development of different types of metastatic cancers.