Read the passage from sugar changed the world.

the diamond and the house: two family treasures, two parts of the story of sugar. we realized that our two family stories—marina's great-grandparents, brought to guyana to replace slaves, and marc's aunt's grandfather, to refine an alternative to that same sugar—were just the beginning of a much larger story about a remarkable substance. it is a story of the movement of millions of people, of fortunes made and lost, of brutality and delight—all because of tiny crystals stirred into our coffee, twirled on top of a cake. sugar, we began to see, changed the world.

what is the purpose of this passage?