With a burgeoning U.S. population of emergent bilingual learners and others who use nondominant language forms, the need for language knowledge among teachers is acute. Beginning from the inside out by examining one's own complex language uses may be a first step toward envisioning and later developing classroom cultures that support diverse language forms for diverse purposes. In all, 262 undergraduate education students used self-reflexive inquiry, documenting ways they and others use language, through language inventories, surveys, and essays. Participants were majority students of color, half bilingual. Students reported awareness of rich diversity and nuances of language uses, purposes, and fluidity across contexts. Although students often used a formal/informal contrast to describe language uses, this distinction was complicated. Understandings of language surfaced in writing as students engaged with linguistically diverse peers and situated their linguistic repertoires in sociopolitical context. Drawing on results and students' reflections on the writings as tools, we offer implications for teacher education.