The cover image depicts (left) an obese (ob/ob) mouse and a normal mouse, and (right) the X-ray crystallographic structure of human leptin W100E. Credits: (left) Oak Ridge
National Laboratory/US Department of Energy/Science Photo Library; (right) F Peelman, L Zabeau, K Moharana, S N Savvides and
J Tavernier, Ghent University, Ghent, Belgium.