A chronic shortage of donor hearts places doctors in an ethical dilemma. Hero Images/Getty Images hide caption
ethics ethics
Molecular markers show structures and cell types within a human embryo, shown here 12 days after fertilization. The epiblast, for example, appears in green. Gist Croft, Alessia Deglincerti, and Ali H. Brivanlou/The Rockefeller University hide caption
Google's self-driving prototype car can be found cruising the streets near the Internet company's Silicon Valley headquarters to test programming responses to a variety of situations. Tony Avelar/AP hide caption
A surgical team at Sooam Biotech in Seoul, South Korea, injects cloned embryos into the uterus of an anesthetized dog. Rob Stein/NPR hide caption
A video still from a Save the Children television fundraising advertisement. Save the Children hide caption
Journalist Brian Williams hosts The Lincoln Awards: A Concert For Veterans & The Military Family on Jan. 7 at John F. Kennedy Center for the Performing Arts in Washington. Recent reports suggest the suspended NBC anchor may have embellished several of his stories. Paul Morigi/Getty Images Entertainment hide caption
When combined with results of other neurological tests, and in the context of a thorough medical history, atrophy of the brain (shown here in an MRI scan) sometimes indicates Alzheimer's. Simon Fraser/Science Source hide caption
Cassandra, age 17, is in a Hartford, Conn., hospital where the state is compelling her to undergo cancer treatment. Cassandra/AP hide caption
Choosing these lemon cupcakes because they're vegan doesn't mean you have to give up your other causes. John Raoux/AP hide caption
Former Virginia Gov. Bob McDonnell arrives at federal court in Richmond on Aug. 28. Steve Helber/AP hide caption