June 21st
1781 Siméon-Denis Poisson, French mathematician and physicist, was born.
1811 Carlo Matteucci, Italian physicist, was born.
1870 Clara Immerwahr, German chemist, was born.
1906 M. S. Tswett submitted the first paper on chromatography; "Physico-chemical studies on chlorophyll. Adsorption behavior", to the Journal of the German Botanical Society.