The Catholic practice of what began during the Middle Ages?

Celibacy? it was formally nailed down during the Council of Trent, which solidified a variety of church practices and was talked about by catechists as though it was something current- like the UN or Watergate (then brand new) not something historical such as Gettyburg address or an obsolete treaty. They used to say- The Council of Trent decrees... present tense! the Council of Trent took place in Italy ( not England) in Elizabethan days! OK, Shakespeare survives too, but that"s literature, not religious doctrine.