If you were alive in 1991 and lived aboveground, odds are good that you owned a Hypercolor T-shirt. By some scientific miracle — a miracle called thermochromic dye — the folks at Hypercolor made T-shirts that changed color with your body temperature. The commercials made it look super cool and sexy; your girlfriend could put her hot hands on your chest and leave a glowing mark. But in reality the hottest parts of your body are usually your armpits. Glowing armpits = not super sexy.
Today, a company called Moving Color manufactures glass decorative tiles coated with thermochromic paint that "come alive" with changing surface temperatures. At room temperature, the tiles are a glossy black, but when you touch the tiles — or hit them with direct light or warm water — the colors transform like the Northern Lights into iridescent blues, pinks and greens. The coolest application has to be the color-shifting shower. The good news for Moving Color is that houses don't have armpits.