This case study highlighting the story of Raphael Lemkin challenges everyone to think deeply about what it will take for individuals, groups, and nations to take up Lemkin's challenge. To make this material accessible for classrooms, this resource includes several components: an introduction by Genocide scholar Omer Bartov; a historical case study on Lemkin and his legacy; questions for student reflection; suggested resources; a series of lesson plans using the case study; and a selection of primary source documents. Born in 1900, Raphael Lemkin, devoted most of his life to a single goal: making the world understand and recognize a crime so horrific that there was not even a word for it. Lemkin took a step toward his goal in 1944 when he coined the word "genocide" which means the destruction of a nation or an ethnic group. He said he had created the word by combining the ancient Greek word "genos" (race, tribe) and the Latin "cide" (killing). In 1948, three years after the concentration camps of World War II had been closed forever, the newly formed United Nations used this new word in a treaty that was intended to prevent any future genocides. Lemkin died a decade later. He had lived long enough to see his word widely accepted and also to see the United Nations treaty, called the Convention on the Prevention and Punishment of the Crime of Genocide adopted by many nations. But, sadly, recent history reminds everyone that laws and treaties are not enough to prevent genocide. Individual sections contain footnotes.