VISTA observations will support research in many astronomical areas. Within our galaxy, VISTA is expected to find many new brown dwarf stars and be able to test ideas about the nature of dark matter. One VISTA survey is designed to find and study huge numbers of variable stars in our galaxy by taking images of the same areas of sky at different times. Using VISTA data astronomers will be able to map the structure of our galaxy in much more detail than ever before. Another VISTA survey will study our neighbouring small galaxies, the Magellanic Clouds, and their surroundings. VISTA data will also be used to create a 3D map of about 5% of the entire observable Universe. Further out, VISTA will be a powerful tool for discovering remote quasars and studying the evolution of galaxies and clusters of galaxies. It will help to probe the nature of dark energy by finding very distant galaxy clusters.