Doing physics involves using and coordinating a variety of external representations – equations, words, graphs, diagrams, manipulatives, computer code, etc – to make sense of the physical world. These external representations are the languages of physics. We use them both to communicate our physics ideas to each other but also as powerful tools for modeling physical systems. In teaching physics, we use some non-professional representations for their pedagogical affordances in supporting physics learners. In this talk, I will talk about my work in understanding how physics students learn to make sense of quantum theory with a variety of external representations. I draw on theories that account for how humans think with their bodies and environments. In particular, I will discuss a collection of studies that explore how students reason about the coherence between discrete and continuous quantum systems and the pedagogical affordances of some specific external representations: algebraic representations of the identity operator, a kinesthetic representation of complex numbers, and Python code.