This conference will be held during April 4 - 7, 2022 to celebrate the 80th birthday of French probabilist Gérard Letac on January 6, 2020. Continuously active and publishing since his first paper appeared in 1964, Letac is now Professor Emeritus at the Institut de Mathématiques de Toulouse, Laboratoire de Statistique et Probabilités of the Université Paul Sabatier. He has authored five books and directed twenty-six PhD students.