As is well-known, every hot object with a temperature above absolute zero, whether artificial or natural, will emit thermal radiation. In nature, many organisms achieve better survival by adjusting their own infrared (IR) radiation. In particular, rattlesnakes can detect prey at night rely on their IR-sensitive pit organs. To threaten rattlesnakes, ground squirrels send out distinct and deceptive infrared tail flagging signals by increasing blood flow to their tails. The total thermal energy radiated from an object is related to its emissivity and temperature, which is based on the Stefan-Boltzmanns law. Consequently, the thermal radiation intensity can be manipulated by adjusting the emissivity or changing the surface temperature to meet different needs. Inspired by natural creatures, the regulation of thermal radiation has been widely used in different fields, including personal thermal management, smart windows, IR camouflage, IR imaging, and so on.