Griffith's experiment was reported in 1928 by Frederick Griffith. This was the first experiment that proved the capability of bacteria to take up by the phenomenon of transformation. Griffith used two strains of Streptococcus pneumoniae the bacteria that infect mice. Smooth strain which was virulent, and the rough strain which was nonvirulent. Griffith discovered that when heat killed smooth strain was mixed with the live rough strain and injected in mice, the mice died. Based on this observation Griffith gave the transforming principle, which states that something was getting transferred from heat killed smooth strain to live rough strain, that made rough strain virulent.