Using bright green lasers and camera equipment, a team of CU Boulder engineers, including Mortenson Center Associate Director Karl Linden, ran an experiment to reveal how tiny water droplets, invisible to the naked eye, are rapidly ejected into the air when a lid-less, public restroom toilet is flushed. Now published in Scientific Reports, it is the first study to directly visualize the resulting aerosol plume and measure the speed and spread of particles within it.