Partly research, partly brainstorm, hope that is okay. basically in my story, a small percentage of humans have been mutated. They still look normal, but I am looking for something measurable that could have changed and is not easily replicatable by the normal humans. That is one part of it at least, the other part is that the "transformation" from human to full mutant has four stages, I would love the measurements to be able to show not only if the person is a mutant, but also if the mutant is stage one, two, three or four. Each stage will look just as human as the non-mutated humans. Basically the way I had imagined it would be detectable is by a device similar to those metal detectors you find on airports. The people walk through those devices and they beep if it is a mutant. But feel free to scrap that bit if you have an idea that would have another method of detection that can quickly be done. My question basically is, what could the device be detecting? It is a fantasy story, but I wouldnt know what is plausible enough to get away with. An idea I had is body temperature for example. A long time ago I read that different emotions have different patterns of body heat. My idea was maybe a specific pattern of body heat or maybe just specifically skin temperature. Another idea was blood tests. I know of various fitness devices that can like check the oxygen in the blood, but I don't know if it could be possible to check the blood without having to get the blood out of the body. (or if blood tests can have results in like, ten seconds) I would love to hear your ideas which might help me with researching things for the final thing to go with, anything goes! Even the silliest things can give me ideas.