It has been 90 years since the existence of gravitational waves was predicted by Einstein in his general theory of relativity. Although Weber started his pioneering work on gravitational waves 45 years ago and large-scale research and development efforts have been mounted since then, gravitional waves have been found to be most elusive. With the progress being made on the ground-based and space-based laser interferometers, there is a good prospect for detecting gravitational waves by the centennial of General Relativity. In this talk, I will review the principle and design of the resonant-mass and laser-interferometer gravitational-wave detectors. I will report the sensitivities reached for cryogenic resonant-mass detectors as well as ground-based laser interferometers, and discuss the prospect of improving their sensitivities further. I will also discuss the progress toward LISA, a space laser-interferometer mission. I will then address the urgent need to develop theoretical templates for various kinds of astrophysical signals.