Researchers at UC, Los Angeles have created cells that go on to form normal T cells out of human embryonic stem cells. What's more, these cells were grown in the absence of animal feeder cells, which are usually needed to sustain embryonic stem cells. Avoiding potential contamination by such feeder cells is an important step in generating cells that can be transplanted into people. The researchers describe a series of steps that drive human embryonic stem cells to begin developing as T cells.