The transatlantic slave trade—a horror that took 12 million enslaved Africans across the Atlantic—began in the 16th century, when Spanish merchants transported Africans to the Caribbean. It was in the 17th century that overseas demand grew exponentially; hundreds of thousands of workers were wanted for cotton and sugar cane plantations. In an exhibition that began its tour in Sao Paulo, 130 artworks have been pulled from over four centuries of art and documents that tell the stories of slaves and their oppressors. Here is a window into worlds of tyranny, hell, and heartbreak. —E.C.