Sometimes the best solution to a complex problem is the simplest one. That’s the approach that the Capillary Structures for Exploration Life Support (Capillary Structures) team took when designing the fluid physics investigation aboard the International Space Station. The Capillary Structures investigation uses capillary action, or the ability for a liquid to flow through a narrow spaces, such as small tubes, to move liquids and gases in microgravity, a task that can’t be tested in Earth’s gravity environment.