This issue brief is the first in a series produced by the Center on Innovations in Learning's League of Innovators. The series will describe, discuss, and analyze policies and practices that enable personalization in education. Topics should be of particular interest to state education agencies and district and school personnel. This first issue overviews the complexities of implementing competency-based education, a component of personalization that has received growing attention. Subsequent issues of the series will present either issue briefs, like this one, or field reports on lessons learned by practitioners recounting the successes and obstacles to success encountered in implementing personalized learning. Neither the issue briefs nor the field reports attempt to present in-depth reviews of the research; for those resources readers are encouraged to access the Center on Innovations in Learning's resource database.