Blended learning is adopted widely in educational settings. Over the past decade, blended courses have increased in higher education (HE), and currently blended learning is expanding in K-12 as well. As blended learning becomes more prevalent, opportunities for research into blended learning are also increasing. Researchers and practitioners need to know the current issues and lines of inquiry prominent in blended learning to direct them to the cutting-edge research and enable them to identify the most pressing problems. This chapter synthesizes and categorizes current blended learning research, with recommendations for future directions. Issues addressed in HE blended learning and K-12 blended learning are identified, compared, and evaluated by reviewing major research on the topic. Finally, future research steps and important research gaps are described.