This topic brief is one in a series on personalized learning prepared for Conversations with Innovators, 2018. Historically, the configuration of public education has been antithetical to variation for and across learners. The structure and process of today's educational system, having cut its teeth during the industrial revolution, emphasizes mass production. Students are to learn the same curriculum, at the same time, and in the same place, within the same prescribed time period. If some students don't learn, or learn more quickly, various attempts may be made to differentiate or individualize instruction; occasionally, these attempts even occur outside the typical school day. However, the basic premise of public education has remained the same for more than a century: large swatches of students doing specific things at a specific time, in a designated place, along one path, at a prescribed pace. In this brief the author describes how the variation of time, place, path, pace, practice, and trace for individual learners is fundamental to true personalization.