Japanese universities are struggling with governmental pressure to ‘replace instruction medium from Japanese to English.’ While a tacit belief is shared among stakeholders that Japanese college classes are taught in Japanese, a literature review revealed that few studies consider empirical data on the realities of ‘languaging’ (the ways language practices enable the instructor and her/his students to communicate one another academically) in college classes. This study aimed to uncover the realities of ‘languaging’ in college science classes to develop a new theoretical framework that is missing from directly relevant previous works, and then report on a number of preliminary case studies in college science classes guided by the framework. The core idea of the new theoretical framework is a ‘changing focus from “language” to “languaging”’ when examining the realities of language practices in academic communication within science classes. Based upon the framework, ‘languaging’ in science classes was analyzed through the theoretical lenses of: (1) instructor’s interventions (e.g., lecturing, blackboard writing, distributed materials) vs. the students’ activities (e.g., note-taking, and questioning); and (2) ‘written’ vs. ‘oral’ languaging. The case studies included are: (1) analyses of college science classes, (2) a comparative study of science professors’ experiences in their college student days and those in their current classes as instructor, (3) a historical study of science classes in an earlier higher education institution, and (4) cross-national comparative case studies on science classes.