Despite an inhospitable appearance, the outflow channel of this small geyser in Yellowstone National Park’s Lower Geyser Basin teems with life. A visible change in the color of this outflow channel from light grey/white to black indicates changes in the chemistry of the water as it flows out of the spring These chemical changes in the channel determine which bacteria cells can live in the different regions of the channel. The orange colors on the left of the main channel are due to pigmented microbes living at the lower temperature of this secondary channel. Credit: David Mead, Lucigen Corp.