In this paper, we aim to differentiate the internal and external horizons of "fusion." "Fusion" in the internal horizon relates to the structure and meaning of the object of learning as experienced by the learner. It clarifies the interrelationships among an object's critical features and aspects. It also illuminates the part-whole relationships of these features and aspects with the object itself. "Fusion" in the external horizon elucidates the relationships between the object of learning and its environment as seen by the learner. These relationships extend beyond the object's boundaries. This paper uses classroom data to show how these two horizons of "fusion" function at different levels and scopes to help learners achieve a deeper understanding of objects of learning.