Optical tweezers, a significant application technology of the laser, are capable of trapping microscopic particles by photon linear momentum transfer. Currently, it is a vital member of the family of micromanipulation tools as well as the precision measurement instrument of pico-Newton force spectroscopy. Its invention does not only aroused vast applications in optics but also plays an important role, as a bridge, in the interdisciplinary research. A short overview on the basic physical principles and concepts of optical trapping over the latest 30 years is provided. Further, some important applications of optical tweezers in cell biology, single molecular biology, the physics of colloidal systems and nano- science are presented as well as the main technical features implied in these applications. Finally, we discuss and expect the perspective of application of optical tweezers in the future.