A 96-well microtiter plate used in an MTT assay. Each column was incubated with different amounts of culture cells, increasing from 500 cells in column 2 (left) to 100.000 cells in column 11 (right), for 72 hours. After a short incubation with MTT, the purple formazan product was extracted using Dimethyl sulfoxide. As can be seen, higher amounts of cells result in higher formazan production and thus a stronger purple colour.