
Leeches - A century after falling out of favor, medicinal leeches are back in hospitals, sucking away on patients' wounds. SETI - Astronomers have their radio telescopes tuned to receive signals from alien worlds. But is anybody out there? Stem Cells Breakthrough - Three separate teams overcome a biomedical hurdle—creating stem cells without the use of human embryos. Profile: Edith Widder - Meet a marine biologist and explorer who has engineered new ways to spy on deep-sea creatures.
Dark Matter - Turns out most of the universe is held together by a mysterious, invisible substance. Of Mice and Memory - Mice placed in enriched environments can recover lost memories, giving hope to those who study Alzheimer's. Profile: Hany Farid - This self-proclaimed "accidental scientist" is a digital detective inventing new ways to tell if photos have been faked. Wisdom of the Crowds - Ask enough people to estimate something, and their combined guesses will get you surprisingly close to the right answer.