About the cover: Cover is based on images of plastic-embedded midsaggital sections of the distal femurs of 12-week-old control (left) and cystic fibrosis transmembrane conductance regulator–deficient (right) mice. The bones were stained with von Kossa and toluidine blue and originally photographed at ×32.5. For more information, see article by Haston and colleagues beginning on page 309.