I first introduce a number of properties related to radiation in our natural surroundings. These properties include thermal radiation, solar irradiation, transparency of the atmosphere, and spectral sensitivity of the human eye and of photosynthesis in plants. The properties are characterized by three important features: spectral selectivity, angular dependence, and time variability. Based on these features, I discuss a number of materials and devices which (i) absorb and transmit solar radiation and visible light, (ii) use the clear sky to cool and to collect dew, (iii) achieve angular selectivity, and (iv) create thermochromic and electrochromic “smart” glazing for energy efficient buildings with good indoor comfort. Whenever possible, the focus is on flexible large-area devices.