There's no denying that thermal images are cool. The colors, for one, make a photograph of light in another spectrum invisible to us very artsy. But thermal images alo carry a lot of information, such as the relative temperature differences, which is why they're so useful in finding insulation deficits, for example. In a living being the heat that's generated reflect the amount of vascular activity, or how much blood flow an area is or isn't getting. In medicine, I've used these to spot infection, strokes, disease, and it's invaluable. So, the hotter an area is, the more blood flow in that area there is.