Mirror cells, if created, would probably multiply in a host organism without much resistance.BSIP/Universal Images Group via Getty ImagesSome scientists trying to create "mirror life" have stopped in their tracks.A mirror microorganism could end up being a major pathogen since our immune systems wouldn't notice it.Mirror-image biology inverts a fundamental property of life on Earth: which way molecules point.Creating "mirror life" could be one of science's greatest breakthroughs, but some researchers who began the effort are now calling for it to stop.No mirror-life microorganisms exist yet.