In this issue:
"Boundaries for a Healthy Planet": Scientists have begun to quantify red-alert levels for environmental problems.
"Faulty Circuits": New discoveries in neuroscience are forcing psychiatrists to rethink the causes of mental illness.
"Regaining Balance with Bionic Ears": Electronic implants in the ear may one day help patients suffering from disabling unsteadiness.
"The Hidden Life of Truffles": Truffles play an essential role in the health of ecosystems.