Economist: Biologists have found a new way to track cells over multiple generations: by inserting fluorescent nanoparticles into the cells and imaging them as they replicate. Previous methods had involved gene insertion, which could damage the cells, and the use of image-recognition software, which produced variable results. By inserting the fluorescent nanoparticles into several dozen cells and taking snapshots over a period of 40 hours, researchers were able to create a time-lapse movie. They also used computer software to track which parent cells divided into which daughter cells. Tracking cell lines, a time-consuming process when done by hand, is vital in determining drug effectiveness.