A miniature ninja throwing star or a surgical device? The microgripper, shown here coming out of a catheter tube, is activated by body heat. The sharp appendages fold up when the device warms up. Evin Gultepe, Gracias Lab, Johns Hopkins University. hide caption

itoggle caption Evin Gultepe, Gracias Lab, Johns Hopkins University.

A microscopy image of a rat pancreas shows the insulin-making cells in green. Masur/Wikimedia.org hide caption

itoggle caption Masur/Wikimedia.org

In this Jan. 18 photo provided by the NYU Langone Medical Center, a technician examines mice to determine their health at the hospital's complex in New York. New York University/AP hide caption

itoggle caption New York University/AP

Musician Jake Orrall performs onstage at the Coachella Valley Music & Arts Festival on April 14. Temporary hearing loss following concerts and other loud events may protect our ears from more permanent damage. Frazer Harrison/Getty Images for Coachella hide caption

itoggle caption Frazer Harrison/Getty Images for Coachella

How much oxygen should severely premature infants receive? A study that sought to answer the question has been criticized for not fully informing parents about the risks to their children. iStockphoto.com hide caption

itoggle caption iStockphoto.com

Scientists hope a new genetically modified rat will help them find Alzheimer's drugs that work on humans. Ryumin Alexander/ITAR-TASS/Landov hide caption

itoggle caption Ryumin Alexander/ITAR-TASS/Landov

An X-ray of electrodes implanted in the brain of a Parkinson's patient at the Cleveland Clinic. Now deep brain stimulation like this is being tried experimentally in a few patients with chronic, serious anorexia. AP hide caption

itoggle caption AP

This image shows a human glial cell (green) among normal mouse glial cells (red). The human cell is larger, sends out more fibers and has more connections than do mouse cells. Mice with this type of human cell implanted in their brains perform better on learning and memory tests than do typical mice. Courtesy of Steven Goldman hide caption

itoggle caption Courtesy of Steven Goldman

Scientists say that understanding how the cocktail party effect works could help people who have trouble deciphering sounds in a noisy environment. Guests make it look easy at a Dolce and Gabbana Lounge party in London in 2010. Paul Jeffers/AP hide caption

itoggle caption Paul Jeffers/AP

A simple switch of ingredients made a big difference in how mice responded to experimental cancer vaccines. Andrei Tchernov/iStockphoto.com hide caption

itoggle caption Andrei Tchernov/iStockphoto.com