Thermogram of feet. Thermograms show the emission of infrared radiation, displaying it as colour- coded surface temperatures. The range shown is from 23 degrees Celsius (purple), through blue, green and yellow, up to 35 degrees Celsius (red). The series of images progress, over time, from left to right. The feet are on a steel floor. The cooling effect of the metal dissipates the feet's warmth, eventually leaving them cold (purple).