Thermochromatic tiles.

An entry into a 2004 design competition dedicated to tiles reimagines your bathroom floor as a multicolored homage to chi. Malaysia-based designer Eugene Low imagines tiles that change color as room temperatures change. "[T]iles can also change colour due to interaction; touching/rubbing tiles or even by breathing on it would change its colour from say blue to orange/red," he writes. So that chilly morning floor gives way to a steam-induced rainbow at showertime or a color shift when you put a pot of tea on the stove. See more entries at designboom's contest page, 100% Tiles.

(Via pasta and vinegar.)