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<jats:p>Researchers once considered the body's network of immune defenses a system unto itself, but they have learned over the past 15 years that it is intimately intertwined with the nervous and endocrine systems. Recently, researchers have begun unraveling the molecular links between these systems, which include the interleukins and hormones such as corticosteroids. And as these connections come to light, they are helping explain some previously mysterious correlations between mental and hormonal states and the immune system.</jats:p>

<jats:p>Every time a jetliner maneuvers, patterns of light and shadow in a device called an interferometer measure the change in angle. Now, photons have a rival for sensing small rotations: interfering atoms. With an atom interferometer, which takes advantage of the wavelike nature of matter described by quantum mechanics, physicists have measured rotations as subtle as a quarter of a degree per hour.</jats:p>

<jats:p>Data communications relies as never before on high-performance lasers for generating the pulses that travel down optical fibers. In his Perspective, Fasol discusses a recently invented laser—the quantum-dot vertical-cavity surface-emitting laser. Made possible by breakthroughs in crystal growth, this laser operates at room temperature and may soon be commercially viable.</jats:p>

<jats:p> Biological systems exhibit molecular handedness: During biosynthesis, predominantly L amino acids rather than D amino acids are incorporated into proteins. The origins of this handedness remain puzzling. In his Perspective, Bada discusses results reported by Cronin and Pizzarello in the same issue (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="951" related-article-type="in-this-issue" vol="275" xlink:href="10.1126/science.275.5302.951" xlink:type="simple">951</jats:related-article> ) showing a slight excess of L amino acids in a well-known extraterrestrial object, the Murchison meteorite. This finding suggests the existence of an enrichment process in cosmochemical environments and could possibly be the source of molecular handedness on Earth. </jats:p>

<jats:p> A mutant <jats:italic>Caenorhabditis elegans</jats:italic> worm, defective in the gene <jats:italic>clk-1</jats:italic> , lives an extraordinarily long time. In this issue, Ewbank <jats:italic>et al</jats:italic> . (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="980" related-article-type="in-this-issue" vol="275" xlink:href="10.1126/science.275.5302.980" xlink:type="simple">980</jats:related-article> ) report the sequence of <jats:italic>clk-1</jats:italic> and find that it is homologous to the yeast gene <jats:italic>CAT5/COQ7</jats:italic> , whose product regulates the transcription of genes that control yeast metabolism. In his Perspective, Guarente describes how these findings fit into a model of aging in which life-span is determined by the accumulation of damage to the organism, perhaps at a rate proportional to metabolism, and the counteracting repair of such damage. </jats:p>