Over the last decade, STEM education research has reflected a turn towards framing disciplinary development in STEM as the repetition and stabilization of situated practices. In this dissertation, I turn further: towards "disciplinary relationships" as a potential focus of analysis. To centralize disciplinary relationships, I use a critical posthumanist approach towards material agency to conceptualize a conversation as an iterative cycle of attention and responsive action. If listening is any type of direction of attention, and speech is any type of action; I consider an agent to be engaged in a conversation (with materials, theory, others, and self) exactly when they are iteratively speaking and listening. By characterizing disciplinary conversations as those conversations that are shaped by the discipline and contribute to shaping the discipline, I focus on how conversations both shape relationships and are shaped by relationships. By considering disciplinary listening, I surface ways that iterative feedback and attention to one's embodiment can inhere in disciplinary practice. Considering disciplinary conversations, I find disciplinary continuity between students' material interactions, their shifting interpersonal relationships, their disciplinary identity, and their embodied sensations and affect. Reconceptualizing disciplinary practices as posthuman conversations also helps to describe the ways that listening carefully for emotional dynamics can be seen as an integral part of STEM rather than separate from STEM practices. In chapter 2, I argue that relational turns such as this one require consideration of a material agency of methodology. I use a postqualitative approach to explore how the framework of disciplinary conversations changes the space of narratives of disciplinary behavior, and describe how relational ontology and postqualitative research impacted our design-based research. In chapter 3, I motivate this turn towards disciplinary relationships as a focus of analysis by making the argument that harm can often inhere in current embodiments of STEM. I describe our research team's emergent modes of inquiry and refinement of the concepts of disciplinary listening and disciplinary speech of more-than-human agents. I operationalize the framework of disciplinary conversations by using postqualitative narrative inquiry to understand the development of one student's disciplinary relationships. I describe four emergent design principles of this relational perspective. In chapter 4, I use a diffractive approach to understand how the ways that mathematics involves a close relationship with our own and others' emotions. Understanding how affect inheres in STEM is important for noticing and responding to the material and affective conditions of our students. Recognizing that affect inheres in STEM requires also questioning where harm may problematically inhere in STEM. To avoid and possibly repair such disciplinary malpractice, a relational turn in STEM education might instead reimagine disciplinary development as the growth of the many relationships that come to define the disciplines. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]