Soldiers participate in physical therapy while using a prosthetic brace called the Intrepid Dynamic Exoskeletal Orthosis (IDEO), which allows them to use and strengthen severely injured legs. John Moore/Getty Images hide caption

itoggle caption John Moore/Getty Images

When Brad Stevens was young, his only "health insurance" was taking tons of vitamins and spending three hours at the gym every day. But after a serious bike accident and an expensive battle with thyroid cancer, the 59-year-old realized nobody's invincible. Heidi de Marco/Kaiser Health News hide caption

itoggle caption Heidi de Marco/Kaiser Health News

Sales of the airliner are flagging, and airlines are retiring their 747 fleets. The end may be near for the original "jumbo jet," but in its day, it offered an experience like no other. Elaine Thompson/AP hide caption

itoggle caption Elaine Thompson/AP

Horace Wilson and other members of his family in a portrait believed to date to the 1860s. He's the mustachioed fellow standing at top right. Courtesy of Abigail Sanborn hide caption

itoggle caption Courtesy of Abigail Sanborn

Mary-Claire King says obscurity gave her the freedom to spend years looking for breast cancer genes. Mary Levin/University of Washington hide caption

itoggle caption Mary Levin/University of Washington

Researchers say intervention in early childhood may help the developing brain compensate by rewiring to work around the trouble spots. iStockphoto hide caption

itoggle caption iStockphoto

Inmates in a recreation yard at the Deuel Vocational Institution in Tracy, Calif. California is trying to address court-ordered reductions in overcrowding with a plan to shift thousands of those convicted of "nonserious" crimes to county jails. Rich Pedroncelli/AP hide caption

itoggle caption Rich Pedroncelli/AP

An oiled murre passes the darkened shoreline near Prince William Sound, Alaska, less than a month after the March 1989 spill. Erik Hill/Anchorage Daily News/MCT/Landov hide caption

itoggle caption Erik Hill/Anchorage Daily News/MCT/Landov

The TALON MAARS (Modular Advanced Armed Robotic System) can be transformed from a weaponized robot to one with an arm and gripper by changing out its modules. PRNewsFoto/Foster-Miller Inc. hide caption

itoggle caption PRNewsFoto/Foster-Miller Inc.

Hanna Rosin says when kids do things that feel risky on a playground, it allows them to conquer a fear and gain independence. Fox Photos/Getty Images hide caption

itoggle caption Fox Photos/Getty Images

Doctors may eventually be able to diagnose "preclinical" Alzheimer's in patients who have abnormal brain scans but who aren't yet showing behavioral symptoms of the disease. iStockphoto hide caption

itoggle caption iStockphoto

Early days: NASA's International Sun-Earth Explorer C (also known as ISEE-3 and ICE) was undergoing testing and evaluation inside the Goddard Space Flight Center's dynamic test chamber when this photo was snapped in 1976. NASA hide caption

itoggle caption NASA

A BigDog robot at Boston Dynamics in 2010. The BigDog is being developed to help soldiers carry heavy equipment in the field. It can follow a human being, walking across wet/sandy/rocky terrain, just like a dog would. Suzanne Kreiter/Boston Globe via Getty Images hide caption

itoggle caption Suzanne Kreiter/Boston Globe via Getty Images