January 18 Live zebrafish (Danio rerio) embryos 4 days after fertilization, with those in the middle ring stained for hemoglobin to detect blood cells. Zebrafish studies have advanced our understanding of heart and blood development. 457 [Image: Alan J. Davidson]

February 8 Will off-the-shelf body parts routinely replace injured or diseased tissue? This representational cover illustration and our special section highlight how far we have come and how far we have yet to go to accomplish this. 995 [Illustration: Cameron Slayden; design: Nathalie Cary]

February 15 A mosaic of confocal images of the entire visual system of the fruit fly Drosophila labeled with an antibody to a photoreceptor-specific protein, Chaoptin. The Gordon Research Conferences on Visual System Development will be held 9 to 14 June 2002 at Salve Regina College, Newport, RI. The schedules for the 2002 Gordon Conferences begin on p. 1327.

March 8 Artist’s impression of the hottest tango in the Universe: A torus formed from the debris of a star spins around a rotating black hole. The black hole feeds energy to the torus, which in turn radiates it away as unseen gravitational waves. At the same time, jets of energy are released along the black hole’s axis of rotation as input to cosmological gamma-ray bursts. 1874 [Image: P. F. A. M. van Putten]

April 19 A mouse embryo 10.5 days after conception stained to show the expression pattern of two proteins, HNF3b (blue) and neurofilament (green). A microscopy technique based on optical projection tomography generates a three-dimensional image (foreground) from fluorescent images of the embryo at multiple stages during rotation (background). 541 [Image: J. Sharpe and U. Ahlgren]

April 26 Complex diseases, such as heart disease, diabetes, and cancer, are among the most common and costly illnesses in Westernized countries. The special section in this issue considers the challenges of sorting out the multiple factors–including lifestyle, diet, infectious agents, and a host of genes–that contribute to disease susceptibility. 685 [Photo illustration: Ann Cutting]

May 24 In a new “cyclic” model, the Universe consists of two infinite three-dimensional membranes (“branes”) that collide and bounce apart every few trillion years (counterclockwise). Our visible world corresponds to the left brane in each frame. Each collision yields new matter and radiation, which cool to form new galaxies and stars. After trillions of years of accelerated expansion, the Universe becomes empty and the cycle begins anew. More information on branes and other multidimensional concepts can be found in the special section in this issue. 1417 [Image: J. Mazeika and P. Steinhardt]

June 7 A time series of leaf development for two members of the Apiaceae family-anise (left) and carrot (right). Differences in blade growth (magenta) and marginal growth (cyan) result in final leaf forms that are simple in anise but dissected in carrot. Recent evolution of leaf form included such changes in secondary morphogenesis. 1858 [Image: T. E. Goliber, S. Kessler, N. R. Sinha]

June 14 Particle-like waves in an excitable medium move according to imposed excitability gradients. Normally unstable, these waves can be stabilized by feedback, with their motion controlled to yield a desired trajectory (red curves). Left and right panels show superpositions of snapshots of experimental and simulated wave behavior, respectively. 2009 [Image: T. Sakurai et al.]

July 19 The head of an embryonic transgenic mouse expressing a stabilized b-catenin protein in neural precursor cells (coronal section, stained with cresyl violet). The cortical surface of the brain is enlarged, with increased surface area and folding of the cortex, indicating that b-catenin can regulate whether neural precursor cells proliferate or differentiate. [Image: A. Chenn]. See page 365 [Image: A. Chenn]

August 9 Polymer vesicles of varied morphology, about 5 to 20 mm across. The copolymers of these vesicle membranes include polyethyleneoxide-polylactic acid (PEO-PLA), which is biodegradable and enables the controlled release of fluorophores such as the anticancer drug doxorubicin. These vesicles are one example of the soft surfaces and interfaces highlighted in the special section in this issue. 961 [Image: F. Ahmed, F. S. Bates, and D. E. Discher]

August 23 Fugu rubripes, the poisonous but delicious Japanese pufferfish. The DNA sequence of the Fugu genome is especially useful because it lacks the “junk” sequences (which do not code for proteins) found in abundance in human DNA. 1301 [Woodcut print by April Vollmer]

September 20 A proposed structure of the He8-carbonyl sulfide (OCS) supermolecule, as construed from vibrational and rotational spectroscopic data. The formation of the first helium solvation layer begins with an equatorial “doughnut” of five helium atoms around the OCS molecule. The spectroscopic study of successive solvation of OCS with helium atoms may shed light on the origins of superfluidity. 2030 [Image: W. J├Ąger and K. Brendel]

October 11 Artist’s impression of two nearby molecules that “couple” (upper image), lose their individualities, and give rise to new spectral features (lower image). By combining high-resolution laser spectroscopy and scanning probe techniques, it is now possible to look deep into the world of fluorescent molecules even if they are only a few nanometers apart. 385 [Image: C. Hettich]

October 25 The synapses that connect neurons in the nervous system are dynamic entities. The special section in this issue focuses on aspects of synapse formation and development and the dynamic processes that occur at synaptic connections throughout the lifetime of an individual. 769 [Image: Kosi Gramatikoff]

November 1 Science, engineering, and technology permeate all areas of modern life. The 2003 AAAS Annual Meeting and Science Innovation Exposition, convening 13 to 18 February in Denver, will explore science in our daily lives in a sterling array of symposia and lectures by leading experts. 1048 [Illustration: Jose Ortega]

November 8 Employees of Afghanistan’s National Museum hid this 6th-to-7th-century A.D. Buddha, excavated in 1937 by French archaeologist Jean Carl in Fondukistan, to prevent its destruction by the Taliban last year. The fate of the country’s artifacts, museums, and archaeological sites is covered in this week’s special section. 1195 [Photo: Chapuis Patrick/Gamma]

November 15 A crystal with 41 holographic filters. Each filter selects one wavelength channel in the fiber communication system at near-infrared wavelengths. When illuminated with white light, each filter diffracts a slightly different spectral band, creating a blue-to-green color gradient. Optical storage is one example of coherence manipulation highlighted in the special section in this issue. 1353 [Photo: Chris Moser and Demetri Psaltis]

December 20 Researchers are discovering that small RNA molecules play a surprising variety of key roles in cells. They can inhibit translation of messenger RNA into protein, cause degradation of other messenger RNAs, and even initiate complete silencing of gene expression from the genome. See the Breakthrough of the Year special section and the accompanying Editorial. 2296 [Illustration: Cameron Slayden]