Particulate matter is an air pollutant that is very damaging to health and extremely common in urban areas. Sotirios Papathanasiou have created this beautiful and yet scary image comparing the size of Particulate Matter (PM2.5 and PM10) against a red blood cell, and pathogens including SARS-CoV-2 (the virus that causes COVID-19). Regular medical masks don’t have much protection effect, if any, against Particulate Matter.