What was the significance of Martin Luther nailing the 95 Theses to the church door in Wittenberg?

Martin Luther nailing the 95 Theses to the church door in Wittenberg in 1517 marked the beginning of the Protestant Reformation. This act challenged the authority of the Catholic Church and sparked widespread debate about religious practices and beliefs. It ultimately led to the formation of new Christian denominations and changed the course of European history.