Differentiation is the process by which stem cells transform into the myriad of different cell types that make up the body. It’s an incredible phenomenon that allows all of us to develop from tiny embryos into complex organisms with countless types of cells that make up our tissues and organ systems. In our bodies, differentiation is exquisitely regulated by a wide variety of signaling pathways and networks, many of which we don’t yet understand. We have, however, learned enough about these processes to artificially direct the differentiation of stem cells outside the body. By adding specific cocktails of chemicals to stem cells in the lab for defined amounts of time, we can coax stem cells into numerous different cell types of our choosing. These so-called directed differentiation protocols have revolutionized the field of tissue engineering and will likely contribute to many more breakthroughs in the future.