Matt Simcik, Associate Professor of Environmental Sciences at the University of Minnesota School of Public Health, in his lab on the University of Minnesota campus in Minneapolis, Minn. on Wednesday, April 4, 2018. He and other scientists are working on a "chemical sponge" that could assist in the clean up of underground pollution. The method uses two types of liquid polymers, which are large man-made molecules. The polymers clean water because they are positively charged — and attract negatively charged pollution particles. (John Autey /Pioneer Press via AP)