In the third and latest adventure from the League of SI Superheroes, the animated online series from NIST, "Mass Hysteria" touches upon a topic—how to redefine basic unit of mass known as the kilogram. It represents a cutting-edge undertaking for researchers working to modernize the worldwide metric measurement system known as International System of Units (SI). Latest episode briefly explores one of the efforts to redefine the kilogram in terms of natural forces called the watt balance.