This paper focuses on the practice of using the question, ‘Do you know X?’This ques- tion has been treated carefully in the community of science communicators (SCs). SCs have the role of connecting scientists and engineers with the general public in exhibition areas in science museums, where they construct dialogues with visitors. The dialogue can be a “delicate ”interaction for two reasons: 1) there is a fundamental difference in the motivation for the dialogue between SCs and visitors in a science museum, and 2) they need to share the goal of dialogue during an ongoing interaction, because they have no specific goal in advance, such as a medical consultation or a business meeting. Therefore, we analyzed the practice of using, ‘Do you know X?’as an example of a “delicate”interaction, based on a conversation analytic approach. We reveal that SCs use ‘Do you know X?’together with other embodied actions for the management of topics in dialogue, such as drawing out the visitors’degree of knowledge or interest in building a “bidirectional”communication. Our analysis also shows that SCs can shape the dialogue to fit the visitors’knowledge or the interest that visitors display publicly. In this sense, it is important for “bidirectional”science communication that not only SCs but also visitors are sensitive to constructing “dialogue”together.