There's a new stem cell in town: induced XEN, or iXEN. Scientists thought for years they were a byproduct of other developing stem cells, but researchers have now determined that they are their own type of cell with their own function, according to a study published last week in the journal Stem Cell Reports.

You've probably heard of pluripotent stem cells, ones with the unique ability to transform into any kind of cell in the body. Scientists wanted to understand them not only to get a sense of the role they play in human development, but also because they could help treat a number of medical conditions in which tissues need to be repaired. For a while, scientists were limited to experimenting with just two types of stem cells: embryonic, which (controversially) come from embryos, and somatic, which are found in other tissues in the body to replace damaged cells.