The closing years of the 20th century have allowed us, for the first time, to seriously discuss interferometric instruments deployed in space. With the express purpose of achieving unprecedented spatial resolution, these missions will lead to new astrophysics. Especially--and most challengely--we expect the carrying out of the first search for terrestrial exoplanets. The detection and study of the latter promises to usher in a new era in science and will affect a broad spectrum of science and technology. Further, the time line for implementation of such instruments is such that it is probably less than 5 - 10 years until we have results from them.