These mutant nematode worm embryos are genetically identical, but fluorescence imaging shows they are not exactly the same. The pink spots are mRNA molecules involved in gut development. Some twins have spots and some don't, which means some will develop guts and others won't. Arjun Raj hide caption

itoggle caption Arjun Raj

The golden mask of Tutankhamen is displayed at the Egyptian Museum in Cairo. New research suggests that the famous pharaoh suffered from numerous ailments, and probably spent much of his life in pain before dying at 19 from the combined effects of malaria and a broken leg. Amr Nabil/AP hide caption

itoggle caption Amr Nabil/AP

The 12-inch gold-plated records contain greetings in 59 languages, samples of music from different cultures and eras, and natural and human-made sounds from Earth. One record is currently 16.89 billion km from Earth, the other is over 13 billion km away. NASA Center: Jet Propulsion Laboratory hide caption

itoggle caption NASA Center: Jet Propulsion Laboratory

An artist's Impression of "Inuk," a 4,000-year-old human whose remains were found in Greenland. Scientists have sequenced most of his DNA using tufts of his hair found in the 1980s. Nuka Godfredsen hide caption

itoggle caption Nuka Godfredsen