[Music throughout] The Wide Field Instrument is the heart of WFIRST. The basic design is the same as telescopes around the world. Light enters through WFIRST's 2.4-meter aperture, and is reflected and focused by the curved main mirror. Additional elements tighten the beam even more, and strip it of stray light rays before it passes through the filter wheel. This wheel has a variety of filters that allow different wavelengths of light to pass through. It spins from one to another depending on what the researcher is looking for. Finally, the focused and filtered light reaches the focal plane, where it creates an image on the detectors. In WFIRST's case, there are 18 detectors, allowing it to create 300-million-pixel images of large patches of the sky. This combination of image size and detail has never been possible on a space-based telescope before, and will make WFIRST an indispensable tool in the future.