Researchers at Stanford University have taken an important step in understanding the chemistry behind the way cells in the brain communicate with one another. Chemists used a laser to trap microscopic membranes in the brain of a sea slug. These membranes are important because they carry chemical signals that convey messages to other brain cells. Richard Zare and his colleagues tore open each membrane and labeled the contents with a dye. The dye attached to specific molecules and glowed when activated by light. This enabled the scientists to read out the contents of individual vesicles. The researchers used sea slugs because their cells are 1000 times larger than those found in humans.