Aspects of the present disclosure are directed to providing and/or controlling electromagnetic radiation. As may be implemented in accordance with one or more embodiments, an apparatus includes a first structure that contains an object, and a second structure that is transparent at solar wavelengths and emissive in the atmospheric electromagnetic radiation transparency window. The second structure operates with the first structure to pass light into the first structure for illuminating the object, and to radiatively cool the object while preserving the object's color.
FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT
 This invention was made with Government support under contract DE-AR0000316 awarded by the Department of Energy. The Government has certain rights in this invention.