In this article, we discuss the contribution of observational methods to understanding the processes involved in triggering interest and establishing engagement. We begin by reviewing the literatures on interest and engagement, noting their similarities, differences, and the utility to each of better understanding the triggering process. We then provide background information about observational methods and a case illustration of their use in a post hoc analysis of observation records collected during an out-of-school biology workshop. In conclusion, we consider the advantages and limitations of observational methods. We suggest that they can offer unique insight into the triggering process. In the post hoc analysis, this includes information about multiple, co-occurring triggers for interest and variation in responses to triggers based on learner characteristics. It is acknowledged that observational methods are not sufficient, but they are necessary; they provide essential detail, especially for understanding the triggering process.