The historical event known as the Reformation challenged the practices of the Catholic Church during the 16th century. Initiated by figures such as Martin Luther, who famously nailed his 95 Theses to a church door in 1517, the Reformation criticized the church's corruption and the sale of indulgences. This movement not only led to the formation of various Protestant denominations but also prompted significant religious, social, and political changes across Europe, ultimately reshaping the landscape of Western Christianity.