The progression of cancer stem cells and their corresponding pathological process. Transformed normal stem cells (SCs), progenitors with self-renewal capacity and differentiated cells after reprogramming are the potential origin of precancerous stem cells (pre-CSCs), whose corresponding pathological process is precancerous condition. Transformation from precancerous stem cells to primary cancer stem cells (pri-CSCs) is a crucial step of cancer initiation. Upon acquiring migrating capacity, primary cancer stem cells transform to migrating cancer stem cells (mig-CSCs) and metastasize to distant organs and cause metastatic cancer. In order to escape from chemoradiotherapy, some of primary cancer stem cells may develop into chemoresistant cancer stem cells (cr-CSCs) and radioresistant cancer stem cells (rr-CSCs). Some transformation steps are marked with gray arrows to indicate that they are speculative with no direct evidence up to date.