Utah startup claims it created human sperm in a lab, made embryos

A Salt Lake City company says it has grown functional human sperm from stem cells—immature cells that can develop into specialized types—and used them to create embryos. The scientists extracted starter cells from tissue samples and developed them into mature sperm in the laboratory. **Worth flagging:** the work has not yet been reviewed by independent experts, so questions about whether others can repeat the results and whether it is safe remain unanswered.