This research has two aims: (1) to bridge a gap in blended learning research--the lack of a systems approach to the understanding of blended learning research and practice, and (2) to promote a more comprehensive understanding of what has been achieved and what needs to be achieved in blended learning research and practice. To achieve these aims, we first assess the strengths and limitations in existing models of blended learning, then propose a framework for blended learning that is grounded in the complex adaptive systems theory. The proposed framework sees blended learning as a system consisting of six essential subsystems, and all the subsystems relate to and interact upon one another. The proposed framework is then applied to the review of 87 empirical studies from the current blended learning literature. The review identifies several gaps in current blended learning research and practice, and advances our understanding of some untapped potential of this new system of learning. We hope that this research will shed light on critical issues in understanding blended learning and in scaling up its implementation in tertiary education.