This is something you haven't seen before: an image of a live, quarter-­millimeter-­long C. elegans worm whose internal organs, tail, and ­pharynx are clearly visible. The image was made by a microscope, under development at MIT, that renders cells and tiny organisms in 3‑D detail by exploiting the ways that different cell structures refract light and combining images made from several angles. In conventional microscopy, the cell or organism being studied must be treated with fixing agents and stains. "Our technique allows you to study cells in their native state with no preparation at all," says Michael Feld, a professor of physics at MIT, who led the microscope's development. In addition to imaging the worm, his group has imaged cervical-cancer cells, which could be seen shriveling up when treated with acetic acid. Because it can show how cells react to different compounds, the technology could be useful in drug screening.