Lorenzo Romano Ameeo Carlo Avogadro di Quaregna e di Cerreto, Count of Quaregna and Cerreto (August 9, 1776 – July 9, 1856) was an Italian savant. He is most noted for his contributions to the theory of molarity and molecular weight and also formulated Avogadro's Law. In tribute to him, the number of elementary entities (atoms, molecules, ions or other particles) in one mole of a substance, 6.022142 x 1023, is known as Avogadro's number.