The science of metallurgy was advanced through the work of Henry Clifton Sorby and others. Sorby pioneered the study of iron and steel under microscope, which paved the way for a scientific understanding of metal and the mass-production of steel. In 1863 he used etching with acid to study the microscopic structure of metals and was the first to understand that a small but precise quantity of carbon gave steel its strength. This paved the way for Henry Bessemer and Robert Forester Mushet to develop the method for mass-producing steel.