This paper is situated within the vast literature that examines issues of under-representation, microaggressions, and social inequities faced by racially and gender diverse students in STEM education. As part of the special issue "Centering Affect and Emotion Toward Justice and Dignity in Science Education," it focuses on analyzing the affective dimensions of racialized students' encounters in postsecondary settings to highlight "affective politics of belonging" to STEM fields within a Canadian context. Research on emotions in science education can benefit from a "process-oriented" view of emotions to better understand how exclusionary boundaries get (re)formed between bodies, which can inform science equity efforts. One major implication of this work is to offer a different analytical tool for approaching notions of "belonging" as commonly employed in science education literature. Through a cultural political analysis of emotions, desires, and affects, we seek to go beyond psycho-social views on belonging as synonymous with understanding students' sense of belonging in STEM. Sense of belonging maintains emotions as interiorized positive feelings, whereby belonging is often employed as a self-explanatory term, if not an end goal, conflating it with (group) identity. Rather, we seek to analyze "how" belonging is affectively constituted in day-to-day encounters between students and within spaces of postsecondary STEM. Careful not to reproduce deterministic and static analyses, we further attend to students' longings and desires for encountering STEM and higher education spaces anew. Finally, we consider some methodological affordances and limitations for attuning to "the affective" and "embodied" in students' responses to an exploratory survey.