Cover photograph: Protein images from rat brain sections, obtained by matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry. Imaging mass spectrometry enables researchers to simultaneously detect hundreds of molecular species and, from this data, map the spatial density for selected ranges of molecular weight. See the Mass Spectrometry Special Feature beginning on page 18088.Image courtesy of Richard Caprioli and Reid Groseclose (Mass Spectrometry Research Center, Vanderbilt University, Nashville, TN).