We're used to a world composed of solids, liquids and gases, but most of the visible universe – 99% of it – is made of plasma. Scientists can study plasmas in the lab, but their devices are limited in size and bounded by walls. When humans launched into the Space Age we gained a new plasma lab, one as big as space itself. Studying plasma opens a window to the stars From studies in space, we've learned much about plasmas and the relation of these charged particles to processes that occur in the cosmos. We've come to realize that this mysterious form of matter holds the key to unlocking many of the puzzles of our universe. By studying processes that occur in Earth's magnetosphere, in interplanetary space, and at other planets, we are better able to appreciate the important role plasma science plays in understanding our plasma universe. This space plasma laboratory is truly a window to the stars.