A lensless microscope the size of a dime might quickly and cheaply scan blood for tumor cells and parasites. In the device created by Changhuei Yang and his team at the California Institute of Technology, light shines on a liquid sample flowing through a narrow channel, below which are one-micron-wide apertures spaced 10 microns apart. The light shines through the holes onto a semiconductor chip studded with sensor pixels similar to those in digital cameras. Objects that float over the apertures block some of the incoming light received by the pixels, which construct an image of the object based on the variations in light intensity. Details down to 0.8 to 0.9 micron are apparent. (Cancer cells typically measure 15 to 30 microns.) With a chip-based microscope, “there's no lens to break,” says Yang, who was inspired by “floaters,” the clumps of dead cells and other debris in the eye. Better yet, they cost about $10 a pop.