Cover image: Low-mass stars forming in the Perseus molecular cloud. This image is a composite of three Spitzer Space Telescope infrared images at 3.6 (blue), 8 (green), and 24 (red) µm. The red point-like objects indicate young stars with circumstellar material. The extended emission originates from warm dust (yellow/red) and large molecules, such as polycyclic aromatic hydrocarbons (green), which are excited by radiation from the young stars. Blue points indicate normal background stars. The Perseus cloud shows a rich variety of gas-phase and solid-state molecules. See the article by van Dishoeck on pages 12249–12256. Image by Lucas Cieza (University of Texas, Austin, TX) based on data from Jes Jørgensen (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA) and Luisa Rebull (Spitzer Science Center, Pasadena, CA), courtesy of NASA/JPL-Caltech (Pasadena, CA).