A historical review of dyes as indicators for analytical chemistry and titrimetric analysis includes the use of color change indicators from their introduction by Gay-Lussac in 1824, to 1920; the use of test papers such as litmus, from the Roman scholar Pliny, to 1940; and the use of biological stains as indicators, from Antony van Leeuwenhoek, who used yellow saffron to dye muscle fibers in 1824, to 1930.