  Hawking radiation is unlikely to be measured from a real black-hole, but can
be tested in laboratory analogues. It was predicted as a consequence of quantum
mechanics and general relativity, but turned out to be more universal. A
refractive index perturbation produce an optical analogue of the black-hole
horizon and Hawking radiation that is made of light. We discuss the central and
recent experiments of the optical analogue, using hands-on physics. We stress
the roles of classical fields, negative frequencies, 'regular optics' and
dispersion. Opportunities and challenges ahead are shortly discussed.
