We investigate the process of becoming an expert in mathematics education through the narratives of Mario, a PhD student in mathematics education, and those of Anna, his young mentor. The narratives examine the initial interactions with mathematics education (specifically, the writing of a conference paper) and explore the motives, interests, and views that frame the process. They also reveal the tensions that drive the change from "being a mathematician" to "being a researcher in mathematics education." On one hand, the described situation provides a typical picture of young Italian researchers in mathematics education, and we highlight the distinctive traits of such experiences. On the other hand, some elements can be generalized to higher education settings. We utilize a participationist lens of analysis and we focus on motives, interests, views, and tensions.