The ability of cancers to grow indefinitely has fueled the idea that cancer and stem cells may have common underlying mechanisms. Detailed gene expression maps have now shown the diversity and distinctiveness in gene expression programs associated with stemness in embryonic and adult stem cells. These maps have further revealed a shared transcriptional program in embryonic stem cells (ESC) and cancer stem cells. Surprisingly, forced activation of an ESC-like gene expression program in adult epithelial cells can reprogram them into human cancer stem cells and achieve pathologic self-renewal. The ability to create induced cancer stem cells (iCSC) may provide opportunities to better define the biology of cancer stem cells in order to trace or eliminate them in human patients.