Google dedicated its doodle on Tuesday to biochemist Søren Peder Lauritz Sørensen. Born on January 9, 1868, this Danish chemist got famous for the introduction of the concept of pH, a scale for measuring acidity and alkalinity of a substance.

pH stands for power of hydrogen, which is a measurement of the hydrogen ion concentration in the body. The doodle, dedicated to Sørensen, is animated game that shows us food item or other substances, and we have to sort it according to its pH values.