Induced pluripotent stem cells allow researchers to ethically create any cell type from an adult cell, raising hopes for regenerative medicine. Eyebrows started to raise recently, though, when labs grew brains with them and turned others into sperm and egg cells.
The race continues between scientists desperately seeking a rationale for harvesting human embryos and those who say, having adult stem cells and iPS cells available, they are unnecessary – and their use is unethical.