Walking along the boardwalk of the Grand Prismatic Spring at Yellowstone National Park, one can appreciate the mesmerizing orange, turquoise and deep blue waters of the spring. Even the steam rising above seems colorful, but this is an optical illusion. The moisture in the steam reflects colors of the spring as well as the brightly colored thermophiles, which are heat-loving bacteria that live there, resulting in the multiple colors of the spring and the steam in turn.