Calvin was of great important for the Reformation because of three points;
-His books were very important, his institutes for example. Or his commentaries about nearly every book of the bible! These commentaries are still used nowadays!
-His correspondence with theologians all over the world. Over 4,000 letters still excist!
-The Academy, A theological college which was founded in 1559. Students from all over the world were trained to become a minister. Calvin`s friend and successor. Theodore Beza was the first rector of the college. A lot of well know students, John Knox(reformer of Scotland), Casper Olevianus(one of the authors of The Heidelberg Catechism), Guido de Brès(author of the Belgian Confesion of Faith) And Marnix of st. Aldegone, a close assistant to Willem of Orange. Were all trained by this college. The doctirines that were pread from the academy came to be called Calvnism.