[3][4][5][6] In 1982, he moved to the United States and worked for fashion brands such as Calvin Klein, Valentino, Gianfranco Ferré and shot with photographers such as Richard Avedon, Giampaolo Barbieri and Herb Ritts.

[4][11] Piazzi joined Women Management Milano, the largest modelling agency in Italy, with offices in Paris and New York as director in 2003, where he became president in 2017.

[17] In 1996, Piazzi arranged the charity event called "Models, Too, Have a Heart" ("Anche le modelle hanno un cuore"), in collaboration with the Anlaids organization to raise funds for the fight against HIV.

[18] He is the founder and ambassador of the non-profit association To Get There ETS, which helps to supply aid to orphaned and HIV-positive children in Uganda and South Sudan.

[18][19][20] Piazzi is an ambassador and volunteer for Progetto Itaca, a foundation that promotes information, prevention, support and rehabilitation programs aimed at people with Mental Health disorders and their families.