Many Southeast Asian countries have been promoting the use of EMI in non-language subjects, including science. Content and Language Integrated Learning (CLIL) is a notion which promotes students’ integration of both content and language. This chapter explores the use of a content analysis technique, an epistemic network analysis to explore how classroom interaction facilitates CLIL. We draw on Lin (2012)‘s ‘rainbow diagram’ to analyse how two Hong Kong science teachers used and expanded communicative resources to promote CLIL. These resources are L1 and L2 every day, oral and academic languages, as well as multimodal representations. A coding scheme is developed based on the ‘rainbow diagram’ from Lin (2012). Afterwards, we illustrate an innovative discourse analysis technique, epistemic network analysis, to characterise the frequency of connections between the codes generated. By qualitatively comparing the epistemic networks between teachers and students in a science practical work setting, we propose that epistemic network analysis can be used to compare the practice of CLIL of experienced and non-experienced teachers, as well as before and after professional development programmes. The strengths and weaknesses of this innovative method are then discussed. Copyright © 2023 selection and editorial matter, Samantha M. Curle and Jack K. H. Pun; individual chapters, the contributors.