The existence of gravitational waves is an important proof of Einstein’s theory of general relativity and took 100 years to be achieved using optical interferometry. This work describes how such a detector works and how it can change the way of seeing the Universe. Kilometers size laser interferometers are being built around the world in the way to make gravitational astronomy; detectors already built in the United States, Italy, and Japan will join efforts with detectors built in Japan and India and provide humanity with the means to see gravitational interactions of black holes and neutron star. Interactions, without these detectors, will be forever out of our sight.