Passive radiative cooling, an emerging technology, provides sustainable, energy-saving solutions. Taking advantage of outer space as a cold sink, a well optical-designed material can passively block incoming heat flux while simultaneously providing cooling effect by emitting thermal radiation. Sub-ambient cooling can be achieved, even under direct solar irradiation. Compared with conventional radiative cooling strategy, passive radiative material leads the way to an eco-friendly cooling without ozone depletion and the greenhouse effect.