Abstract: The invention of the laser brought us into the era of light communication, light storage, light displays, and so on. High quality lasers, with low threshold, high efficiency, high brightness, high speed and small volume, have become essential for future applications. However, all the above-mentioned properties have limitations in traditional laser physics and technology. Photonic crystals combined with modern laser physics and technology have opened a way to overcome the bottleneck of such limitations. Based on the manipulation of photon states in photonic crystals it is now possible to increase the spontaneous emission rates so that a thresholdless laser will finally become realizable, and the simultaneous achievement of an ultra-high cavity quality factor and ultra-low cavity volume will result in lasers with much greater brightness and higher speed. It can thus be expected that photonic crystal science and technology will become the basis of future opto-electronics. We describe the use of photonic crystals in semiconductor lasers, whereby the laser characteristics are greatly enhanced, and discuss the potential applications and future developments of photonic crystal lasers.