Billowing clouds of gas and dust fill this Spitzer Space Telescope image of part of the Milky Way galaxy. Most of this material isn't visible at optical wavelengths, but it does glow in the infrared, which Spitzer investigates. This material forms the interstellar medium, a thin mixture that permeates the space between stars. Especially cold dust forms dark ribbons in this false-color image. The dust in those lanes may someday collapse to give birth to new stars. [NASA/JPL/Caltech]