Beta eye-lets

Looking through the lens of his confocal microscope, Per-Olof Berggren peers at the colonies of beta cells that he injected just in front of the mouse's iris. He watches its dark eyes light up with different fluorescent labels that mark the physiological processes of the transplanted beta islet cells. It's a procedure he hopes could one day be used in humans to treat diabetes. But for now, Berggren is focused on the basic science of the technique he designed. "If you can use the eye to look out," says Berggren, "why not use the eye as a body window to look in?"