Teachers need an understanding of the nature of science (NOS) to enable them to incorporate NOS into their teaching of science. The current study examines the usefulness of a strategy for challenging or changing teachers' understandings of NOS. The teachers who participated in this study were 10 initial teacher education chemistry students and six experienced teachers from secondary and primary schools who were introduced to an explicit and reflective activity, a dramatic reading about a historical scientific development. Concept maps were used before and after the activity to assess teachers' knowledge of NOS. The participants also took part in a focus group interview to establish whether they perceived the activity as useful in developing their own understanding of NOS. Initial analysis led us to ask another group, comprising seven initial teacher education chemistry students, to take part in a modified study. These participants not only completed the same tasks as the previous participants but also completed a written reflection commenting on whether the activity and focus group discussion enhanced their understanding of NOS. Both Lederman et al.'s ("Journal of Research in Science Teaching," 39(6), 497-521, 2002) concepts of NOS and notions of "naive" and "informed" understandings of NOS and Hay's ("Studies in Higher Education," 32(1), 39-57, 2007) notions of "surface" and "deep" learning were used as frameworks to examine the participants' specific understandings of NOS and the depth of their learning. The ways in which participants' understandings of NOS were broadened or changed by taking part in the dramatic reading are presented. The impact of the data-gathering tools on the participants' professional learning is also discussed.