Hawking radiation is electromagnetic radiation (EMR) emitted from a black hole through a particular process worked out by Steven Hawking. This was surprising because black holes "allow nothing to escape", including EMR. The process is the consequence of quantum theory overcoming what general relativity would otherwise dictate. There are various ways to conceive the mechanism, a common one being that quantum fluctuations just outside the event horizon produce a pair of virtual particles, which happen to be such that one escapes and the other falls through event horizon. With this permanent separation, the particles cannot recombine (annihilation would have been the typical result) and the particle that escaped effectively becomes "no longer virtual". Another way to conceive the mechanism involves quantum tunneling outward through the event horizon. The resulting EMR spectral energy distribution is worked out to be black-body radiation as if black holes have temperatures proportional to their mass. A consequence is that unless mass continues falling into a black hole at a sufficient rate, the black hole grows smaller and given enough time, eventually dissolves into nothing.