To build future optical information superhighways, "photonic engineering" should be a common practice just like today's electrical engineering. As Purcell proposed in 1946, the radiation rate of photons from an excited atom can be controlled by modifying the space that surrounds the atom. Should this photon tailoring be positively adapted, dramatic improvement of photonic devices can be expected. For example, zero-threshold lasers, high-efficiency light-emitting diodes, and tight-bending waveguides for optical integrated circuits could be realized in the not-too-distant future. This article discuses the photonic crystal, which is expected to lead us through this new and expanding world of nanophotonics.