Up to now, if scientists wanted to study blood cells, algae, or bacteria under the microscope, they had to mount these cells on a substrate such as a glass slide. Physicists have now developed a method that traps biological cells with a laser beam enabling them to study them at very high resolutions. In science fiction books and films, the principle is known as the ‘tractor beam’. Using this procedure, the physicists have obtained superresolution images of the DNA in single bacteria.