Sometime in the mid-2020s, the United States plans to launch a new member of its fleet of space observatories, one with a field of view 100 times more powerful than the Hubble Space Telescope. The Wide-Field Infrared Survey Telescope, or WFIRST, will spend six years scanning the universe. It will scour the Milky Way in search of hundreds of more exoplanets, and it will soak up the light from distant stars in the hope of understanding, even just a little, the great mystery that is dark energy.