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.
Stem cells continue to show promise for dramatic healings, but reporters don't always clarify what lived or died to produce the cells. Adult stem cells inhabit all living humans; embryonic or fetal stem cells require a human death.
Surely one of the great mysteries of human life is how a single fertilized egg cell grows to an adult, with a brain sporting hundreds of billions of functional connections supporting abstract thought.