[[Файл:Max Planck Wirkungsquantums 20050815.jpg|thumb|right|A commemoration plaque for [[Max Planck]] on his discovery of Planck's constant, in front of [[Humboldt University]], [[Berlin]]. English translation: "Max Planck, discoverer of the elementary quantum of action ''h'', taught in this building from 1889 to 1928."]]