Feature

  1. Earth

    Counterintuitive Toxicity

    Toxicologists risk missing important health effects, both good and bad, if they don't begin regularly probing the impacts of very low doses of poisons.

    By Janet Raloff
  2. Humans

    Weighing In on City Planning

    Accumulating evidence suggests that urban sprawl discourages physical activity and may thereby contribute to obesity and related health problems.

    By Ben Harder
  3. Computing

    Digital Fingerprints

    New methods to identify Internet users by their behavior can uncover criminals online, but these techniques may also track millions of innocent users.

    By Julie Rehmeyer
  4. Physics

    Cellular Contortionist

    Mounting, but controversial, evidence suggests that DNA flexes more easily than previously thought, with potentially important implications for genetics, cell biology, and nanotechnology.