**ONE OF THE WORLD'S FASTEST COMPUTERS HELPS UNRAVEL MYSTERIES OF THE UNIVERSE: In this Review, Hut and Makino describe how the GRAPE family of special purpose supercomputers has been used with great success in studying star cluster evolution, the collision of black holes, the formation of planets and galaxies, and the evolution of galaxy clusters. Before the GRAPE computers were developed, astrophysicists in need of computers that could execute highly complex computations had been disappointed to find that computer speed lagged far behind expectations. (The number of transistors crammed onto a single computer chip doubles every 1.5 years, thus initially creating expectations that computer speed would increase dramatically. But this has not been the case.) The lag results in part because computer chips are generalized and required to perform multiple tasks that may not be related to the same goal. So, as Hut and Makino describe, a group of astrophysicists at the University of Tokyo took matters into their own hands over ten years ago and created a chip with one specific purpose: to keep track of the gravitational interactions between millions or billions of particles over the complex models of galaxies full of stars or dusty disks full of particles that accrete to form planets. The project resulted in the GRAPE (short for gravity pipe) family of special-purpose hardware that perform all other calculations in the model. One of the computers, the GRAPE-4, was the world's fastest computer from 1995 to 1997. These fast and efficient computers have allowed astrophysicists to simulate the complex interactions of particles and understand in far clearer detail how planets may form, how galaxies may collide, and how star clusters may grow. ORDER ARTICLE #6: "Astrophysics on the GRAPE Family of Special-Purpose Computers" by P. Hut at Institute for Advanced Study in Princeton, NJ; J. Makino at U. of Tokyo in Tokyo, Japan. CONTACT: Piet Hut at 609-734-8075 (phone), 609-924-8399 (fax), or piet@ias.edu (e-mail) http://xxx.lanl.gov/abs/astro-ph/9811418