February 11 COVER Albert Einstein early in his career (circa 1910). In 1905, Einstein published five seminal papers on the photoelectric effect, special relativity, and Brownian motion. We celebrate the 2005 World Year of Physics that honors Einstein’s achievements with a special section focusing on some of the challenges that remain in physics. See page 865 [Photo: Hulton Archive/Getty Images]

March 4 COVER Artist’s view of a human T cell as a globe, with the chemokine CCL3L1 shielding the cell from infection by HIV-1 (circles with red spikes) by virtue of its interaction with the HIV coreceptor CCR5 (yellow). CCL3L1 is represented by green circles emanating from green bands on chromosome 17, with the intensity indicating differences in gene dose (fluorescence in situ hybridization courtesy of Robin Leach). See page 1434. [Image: S. K. Ahuja and D. Baker]

March 11 COVER False-color image of the north polar region of Mars in summer, showing its composition as inferred by the OMEGA/Mars Express visible and near-infrared imager. The cap is made of water ice (blue) mixed with mineral grains (shades of gray), with dark zones of ice-free minerals within which vast areas of gypsum (red), a hydrated sulfate, have been discovered. See page 1574. [Image: © Institut d’Astrophysique Spatiale]

March 18 COVER Repeated images of an optical cross section through a Drosophila wing epithelium very early in development, illustrating that regions lacking a morphogenetic signal (deprived regions shown in blue) also lack a well-organized apical cytoskeleton (yellow band, microtubules and F-actin together). As described on page 1785, extracellular signaling pathways can direct appendage development through position-specific effects on epithelial architecture. [Image: M. Gibson]

April 8 COVER A montage of pseudo-colored Arabidopsis inflorescence apices as observed by electron microscopy; wild types and leafy mutants alternate, starting with a wild type at the top left. The LEAFY gene is critical for acquisition of floral identity in angiosperms and sporophyte development in mosses. Changes in the DNA binding domain are responsible for differences in the biological activity of LEAFY between mosses and flowering plants. See page 260. [Image: A. Maizel and J. Berger]

April 15 COVER A human retina (center) with complement factor H, a regulator in innate immunity, shown in red. As described on page 385, individuals with a variant form of this factor have an increased risk of age-related macular degeneration (AMD), as shown in photos at left and right. Also shown in the center retina, from a deceased person without AMD, are cell nuclei (blue), lipofuscin granules (yellow) in retinal pigment epithelium, and elastin (green) in Bruch’s membrane and large blood vessels. [Images: J. Tsai; F. Ferris and E. Chew; C. Zeiss; background image: Jupiter Images]

April 29 COVER A ring of 40 helices (yellow) forms the rotor of a bacterial enzyme that cleaves adenosine triphosphate (ATP). See page 654. The rotor is part of a mechanism for transporting sodium ions (red spheres) out of the cell. In eukaryotes, similar rotors generate ion gradients for protein trafficking, endocytosis, and neurotransmitter release, and they help to make ATP. [Image: M. G. Montgomery]

May 20 COVER Spectral-element simulation of surface ground velocities (red up, blue down) 15.8 minutes after rupture initiation of the great 2004 Sumatra-Andaman earthquake. Seismogram shows 160 minutes of actual-amplitude vertical ground displacement recorded at Pallekele, Sri Lanka. See page 1127. [Image: S. Lombeyda, Caltech Center for Advanced Computing Research; V. Hjorleifsdottir and J. Tromp, Caltech Seismological Laboratory; R. Aster]

May 27 COVER A collage, based on botanical drawings of the 17th to 19th centuries, illustrating the different categories of rapid plant movement: Dionea muscipula uses a snap buckling movement to capture prey; Astromeria uses an explosive fracture to disperse its seeds ballistically; and Pharbitis nil twirls its tendrils in search of support through swelling. Also shown are formulas (see page 1308) for the physical limits of rapid plant and fungal movements. [Image: Ellen Skotheim]

June 10 COVER Once neglected, studies of women’s health are finally coming of age. A special section explores new findings on female-male differences in health and sexuality, as well as conditions specific to women. [Image: Getty Images]

June 17 COVER Human embryonic stem cells derived by nuclear transfer (green moon) match the donor cells genetically and immunologically (human leukocyte antigen data sets represent bamboo), regardless of the age, sex, or disease status of the donor of the nucleus. The patient-specific cell lines described on page 1777 may aid in the discovery of complex disease mechanisms and human developmental processes. [Image: H. Qidwai]

June 24 COVER Molecular-beam flame sampling. A flat flame (blue) from a sintered metal burner (bottom) produces gases that are sampled through a small aperture in a quartz cone. These gases can then be analyzed by synchrotron-photoionization mass spectrometry, which has revealed previously undetected combustion intermediates. See page 1887. [Photo: Sandia National Laboratories]

July 8 COVER Scanning electron micrograph of an etched sample of the mineral skeleton of the marine glass sponge (genus Euplectella), showing the laminated silica cement that holds glassy fibers in place. The design principles of this sophisticated, mechanically stable structure are described on page 275. [Image: J. C. Weaver, D. E. Morse, and J. Aizenberg]

July 15 COVER Colored scanning electron micrograph of Trypanosoma brucei (blue) among red blood cells. A special section in this issue presents the genomes of three insect-transmitted trypanosomatid parasites that cause chronic and ultimately fatal infections in humans and livestock, for which few safe therapies exist. Several accompanying articles discuss trypanosomatid comparative biology and strategies for control. See page 399. [Image: Eye of Science/Photo Researchers Inc.]

July 22 COVER A surface representation of human Toll-like receptor 3, derived from the x-ray crystal structure and shown on a cell membrane. The glycosylated Toll-like receptor dimer (green with pink sugars) recognizes double-stranded RNA (orange) from microbial pathogens such as viruses (lavender). Binding of the RNA to the receptor activates the innate immune system. The structure is described on page 581. [Image: J. Choe, M. Pique, and I. A. Wilson]

July 29 COVER Identifying new medicines and bringing them to market is a huge gamble–and the stakes are high. A special section examines the world of drug discovery and the scientists who work in it. See page 721. [Illustration: Stephen R. Wagner]

August 5 COVER The integral membrane portion of the mammalian Shaker family potassium channel, Kv1.2, viewed from the extracellular solution. The channel is gradually colored from its amino terminus (red) to its carboxyl terminus (blue) and is illustrated with sticks. A green sphere represents a potassium ion in the central ion conduction pathway. See page 897. [Image: S. B. Long et al.]

August 19 COVER A crystal of colloidal particles far below its melting temperature. A grain boundary rises diagonally from left to right, separating sections of the crystal with different orientations. Circles denote the time-averaged position of each particle, with red indicating a lower degree and blue a higher degree of positional fluctuation about its equilibrium position. See page 1207. [Image: A. M. Alsayed et al.]

September 9 COVER Test logic circuits for next-generation computing technology. Thin magnetic nanowires can be used to perform digital logic functions using spintronics, an alternative to traditional semiconductor electronics. See page 1688. [Image: Imperial College London]

October 7 COVER A set of Viewpoints in this issue of Science highlights the signaling pathways that control the cellular life cycle, from undifferentiated stem cells to cell death by apoptosis. These signaling pathways are represented by canonical pathways, as well as pathways specific to rice, Arabidopsis, and humans, in the Connections Maps database at Science‘s STKE. [Illustration: Chris Bickel]

October 21 COVER The AAAS Annual Meeting is widely recognized as the world’s premier showcase of advances in science and technology and issues in science policy and education. The 2006 meeting, 16 to 20 February in St. Louis, will attract more than 9000 participants, including media from around the world. [Image: Photonica/ Getty Images]

October 28 COVER The tip of a growing shoot from an Arabidopsis thaliana plant in which a developmental gene, CLAVATA3, has been disabled. The result is overgrowth of the stem cells (green) in the shoot and floral meristems. See page 663. [Image: G. V. Reddy]

November 18 COVER Confocal micrograph of an artificial compound eye produced by biologically inspired optical system synthesis. Each microlens is individually self-aligned with an artificial cone and a waveguide. See page 1148. [Image: K. Jeong]

December 2 COVER A variety of proteinaceous pores translocate ions, proteins, and DNA across cell membranes. A special section in this issue looks at how they accomplish this essential task. [Image: Chris Bickel]

December 16 COVER The cellular changes of lightly pigmented golden zebrafish show a striking resemblance to those of lighter skinned humans. The zebrafish pigment gene slc24a5 is functionally conserved across evolution; a single base change in its human ortholog may play a role in pigment variation in human populations. See page 1782. [Image: J. Mest and J. Cheng]