A.J. Welch can turn skin transparent but, no, he explains with a laugh, he cannot make you look like one of those old "Visible Man" science toys. What Welch, a biomedical engineer at the University of Texas at Austin, and his colleagues can do is nonetheless amazing: They can create temporary windows where they can see right through the outer skin of rats and guinea pigs.
The trick is an injection of glycerol under the animals' epidermis. Glycerol drives out the water molecules that normally scatter light and render skin opaque. Because glycerol has nearly the same index of refraction as collagen, the common protein in skin, light travels in a straighter line through treated cells. In a few minutes, the skin becomes transparent up to a millimeter or two deep— far enough to make blood vessels visible. Water gradually seeps back into the cells, so the skin fogs up ...
