2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/17273In this talk I will describe the deep influence Planck had on the development of statistical mechanics. At this end I will first outline the theoretical situation of statistical mechanics before Planck. I will then describe his main contributions to this field and the progresses obtained as an immediate consequence of his work. I will also outline the later evolution of statistical mechanics in relation with Planck's work. I will finally report on a still unsolved problem in statistical mechanics, historically related to the properties of black-body radiation.11 pages, historical talk given at the Accademia dei Lincei at the conference on Max PlanckStatistical MechanicsHigh Energy Physics - TheoryHistory and Philosophy of Physicstext