January 1 COVER Crystal structure of a molybdenum oxide nanowheel, 2.6 nanometers in diameter, around a smaller molybdenum oxide cluster. Miras et al. (page 72; related Perspective page 38) used a controlled-flow reactor to show that the central core serves as a transient template for the self-assembly of the nanowheel and is ultimately ejected to yield a hollow finished product. Image: Leroy Cronin, Ryo Tsunashima, Haralampos Miras/ University of Glasgow

January 15 COVER Dendritic cells of the immune system recognize and bind bacteria and other microbes by means of receptors expressed on the dendritic cell membrane and within the cell, thus triggering an immune response. Microbial sensing is associated with the innate arm of the immune system, and recent developments in this area are described in the special section starting on page 283. Image: Chris Bickel

February 12 COVER Bags of rice await export from India to Europe. As the global population climbs to a projected peak of some 9 billion in 2050, concerns about food security are growing. A special section beginning on page 797 examines the causes of food insecurity and some solutions, and the implications of climate change and energy use for feeding the world. Photo: Simon Rawles/Alamy

February 19 COVER “Branching Morphogenesis,” an installation made from more than 75,000 interconnected cable zip ties, illustrates the predicted forces generated by human lung endothelial cells as they form networks within an extracellular matrix over time. Winners of the 2009 Science/NSF International Science & Engineering Visualization Challenge are featured in a special section starting on page 945. Image: Jenny E. Sabin; installation: Peter Lloyd Jones, Jenny E. Sabin, Andrew Lucia, Annette Fierro/Sabin+Jones LabStudio, University of Pennsylvania

March 19 COVER Saturn and its rings as seen by the Cassini orbiter. Saturn’s rings contain innumerable chunks of water ice polluted by material of varying color and composition. The massive B ring (bottom) and the tenuous C ring (closest to the planet) are dominated by unexplained structure. Saturn’s yellowish appearance signifies a deep cloud layer beneath seasonal haze. See pages 1470 and 1476. Image: NASA/JPL/CICLOPS

March 26 COVER Sunset for silicon? The push toward electronics that are smaller, faster, and more flexible requires either new inorganic and organic materials or new functionality for silicon and new transistor designs. See the special section beginning on page 1595. Image: Medioimages/Photodisc

April 2 COVER An array of alternating open and closed potassium channel pores. A Research Article on page 67 describes a mechanism by which cell membrane voltage, through the action of protein voltage sensors, controls ion channel opening and closing to produce electrical impulses in the nervous system. Credit: Xiao Tao, Rockefeller University

April 23 COVER Children learning science, like these 7-year-olds tackling chemistry in 1948, must work through their mistakes and misconceptions. The route to science literacy involves reading, debate, presentation, and writing. See the special section beginning on page 447. Photo: Nina Leen/Time Life Pictures/Getty Images

May 7 COVER Three Neandertal bone fragments, approximately 40,000 years old, from Vindija Cave, Croatia (shown to scale). DNA extracted from these bones was used to generate a draft sequence of the Neandertal genome, which was then compared to the genomes of five present-day humans. See page 710 and www.sciencemag.org/special/neandertal/. Photo: Christine Verna/Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology

June 11 COVER Rows of marching soldiers will risk their lives to defeat the enemy and protect their country during intergroup conflicts. This combination of self-sacrifice and aggression toward competing groups is known as parochial altruism. A Report on page 1408 reveals that this behavior is regulated by oxytocin, a short peptide produced in the hypothalamus and known to promote in-group trust and cooperation.[Photo: Fernando Bueno/Getty Images]

June 25 COVER Three-dimensional representation of the emission of electrons from a neon atom upon absorption of a photon from an attosecond extreme ultraviolet pulse. The orange surface plot represents the resulting electron energy distribution, which, when probed by an ultrashort light wave (yellow line), reveals an unexpected time delay between the emission of electrons from different atomic orbitals. See page 1658. Image: Christian Hackenberger/Ludwig-Maximilians-Universität, Munich, Germany

July 23 COVER Retinal photoreceptors from a mouse model of retinitis pigmentosa, a degenerative disease that leads to blindness, following gene therapy. Expression of a microbial light-activated ion pump (green) in damaged cone cells restored light sensitivity to the diseased retinas. An activated ganglion cell, which relays visual information to the brain, is shown in magenta (diameter, ~12 µm). See page 413. Image: Volker Busskamp and Botond Roska/Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland

August 20 COVER Immuno–electron micrograph of a plastid-dividing ring (diameter ~500 nm), a structure required for chloroplast division, isolated from the unicellular alga Cyanidioschyzon merolae. Immunogold particles (black dots) indicate localization of the glycosyltransferase protein PDR1 (protein dividing ring 1), which forms a ring with carbohydrates that constricts to physically divide the chloroplast. See page 949. Image: Yamato Yoshida, Haruko Kuroiwa, Tsuneyoshi Kuroiwa/Research Information Center for Extremophile, Rikkyo University, Tokyo, Japan

September 10 COVER Seeds in storage containers destined for the Millennium Seed Bank, a conservation project run by Kew Gardens, UK, which now houses 10 percent of the world?s plant species as seeds. The conservation of biodiversity is in the spotlight as scientists, nongovernmental organizations, and politicians prepare for the Convention on Biological Diversity in Nagoya, Japan, in October 2010. See the special News Focus section beginning on page 1272 and the Review on page 1298. Photo: Bryan and Cherry Alexander/Alamy

October 1 COVER An artist?s rendition of the Kepler-9 system in which two Saturn-size planets transit the same star. The radii of the planets are roughly 8% of the radius of the star, which itself is 10% larger in radius than our Sun. Timing variations in the transits of these planets provide a signature of their gravitational interaction and can be used to establish their masses. See page 51. Image: NASA/Ames/JPL Caltech/T. Pyle

October 8 COVER Confocal microscopy image of human ovarian clear cell carcinoma tissue. Cancerous epithelial cells are stained bright red (top half of image) and are bordered by supporting stromal cells (bottom and upper right corner). Cell nuclei are stained purple. Genetic analysis by Jones et al. suggests that aberrant chromatin remodeling contributes to the pathogenesis of this cancer. See page 228. Image: Ie-Ming Shih and Bin Guan

October 15 COVER False-color scanning electron microscopy image of a cluster of L-cystine crystals captured on a porous fi ltration membrane after growth in the presence of a growth inhibitor. The tapered needles result from binding of the inhibitor at the crystal surface, which reduces the crystal growth rate and the crystal size (the cluster is ~95 μm across). This suggests that inhibitors might be designed to prevent or limit the formation of L-cystine kidney stones. See page 337. Image: Zhihua An and Timothy G. Bromage/New York University

October 22 COVER Surface temperature map of the south polar region of the Moon acquired by the Lunar Reconnaissance Orbiter Diviner Lunar Radiometer Experiment. Blue and violet areas are intensely cold impact craters. The Lunar Crater Observation and Sensing Satellite (LCROSS) spacecraft struck one of these craters (near the center of the frame), revealing the presence of water ice and other frozen volatiles. See the six research papers beginning on page 463. Image: David A. Paige/UCLA/JPL/GSFC/NASA

November 12 COVER Neck region of an emperor penguin (Aptenodytes forsteri), the skin of which was collected in 1929 on Richard E. Byrd?s first Antarctic expedition. The ~36-million-year-old feathers of a giant fossil penguin from Peru indicate that feather shape evolved early in the penguin lineage, but that adult penguin coloration has shifted from a color palette that included reddish-browns and grays. See page 954. Photo: Julia Clarke, University of Texas at Austin

November 26 COVER A domestic cat (Felis catus) laps milk by lowering its tongue to touch the liquid surface and then rapidly pulling it up, creating a liquid column, the top of which the animal captures in its mouth before gravity draws it down. Measurements of lapping frequency in domestic and wild cats suggest that this mechanism is conserved among felines and that lapping frequency is tuned to maximize the ingested volume per lap. See page 1231. Photo: Micaela Pilotto, Pedro Reis, Roman Stocker