In this paper, I argue for the relevance of structured part-whole configurations in the domain of events. The evidence comes from the well-known event-internal/external distinction, which concerns mutliplicative adverbials quantifying either over separate occasions or occasion-internal acts, respectively (e.g., Cusic 1981, Andrews 1983, Cinque 1999, Zhang 2017). In order to capture this distinction, I postulate that the relationship between the two categories is based on a part-whole relation. In particular, inspired by proposals advocating the role of eventive higher-order units (Landman 2006, Henderson 2017) and building on the theories of (Grimm 2012) and (Mazzola 2019), I propose to extend mereotopology to the domain of events. I argue that this allows for capturing acts as simplex events conceptualized as bounded integrated MSSC wholes, whereas occasions as clusters, i.e., temporally structured configurations, of such simplex events.