Who is Martin Luther and John Calvin from Trial and Triumph: Stories from Church History and what is their importance?

Luther began the Reformation when he nailed his 95 theses to the door of the Wittenburg Chapel in October of 1517. His disagreements with the Roman Catholic hierarchy were initially merely scholarly but soon exploded and evolved into something much broader.

John Calvin took up Luther's ideas a generation later as a departure point for his own theological thinking and developed a variation of Protestantism known as Calvinism which in turn produced the Presbyterian denomination of which the author is a member.