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Chameleons have a diagnostic thermal protection that enables them to live under various conditions. Our developed special radiative control therefore is inspired by the chameleon thermal protection ability by imitating its two superposed layers as two pigment particles in one coating layer. One particle imitates a chameleon superficial surface for color control (visible light), and another particle imitates a deep surface to reflect solar irradiation, especially in the near-infrared region. Optical modeling allows us to optimally design the particle size and volume fraction. Experimental evaluation shows that the desired spectral reflectance, i.e., low in the VIS region and high in NIR region, can be achieved. Comparison between the measured and calculated reflectances shows that control of the particle size and dispersion/aggregation of particle cloud is important in improving the thermal-protection performance of the coating. Using our developed coating, the interior temperature decreases and the cooling load is reduced while keeping the dark tone of the object.Spectral control has been developed as an important technology in thermal engineering. In nature, such complex radiative control has already been realized by morpho butterflies 1-3 , chameleons 4 , and other animals [5][6][7][8][9][10] . A chameleon controls light by dispersion (or aggregation) of pigment-containing organelles within its dermal chromatophores. It organizes iridophores into two superposed layers to create efficient camouflage with spectacular display while potentially providing a passive thermal protection. Within the superficial thick layer of the dermal iridophores, chameleons change color [visible (VIS) light] by active tuning a lattice of guanine nanocrystals. A denser population of iridophores with large crystals reflects a substantial proportion of sunlight, especially in the near-infrared (NIR) range (Fig. 1a).The radiative control by a chameleon, which controls VIS light and reflects NIR light, is ideal in many cases. For example, products such as cars and buildings 11-14 are usually exposed to too much sunlight. In many cases, dark-color coatings are preferably used in these products for appearance purposes. However, these dark coatings absorb a large amount of solar irradiation in the VIS and NIR regions. Therefore, the interior temperature becomes high and creates a large cooling load in air-conditioning systems. The resultant energy consumption contributes to environmental problems such as the greenhouse effect 15 and urban heat islands 16 . In a situation where a surface must be kept cool when exposed to sunlight, the surface should have maximum solar-energy reflectance. We designed a bio-inspired Chameleon Cool Coating (C 3 ) by imitating two superposed layers as two pigment particles in one coating layer (Fig. 1b) to simultaneously achieve two contradictory properties: "black" and "cool. " One particle controls the color (VIS light), and the other particle reflects NIR light. Single layer makes us easy to introduce our coa...

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