Researchers of science education, historians, and philosophers of science agree that the teaching of nature of science (NOS) is important to be integrated into K-12 classes. Our previous research showed that NOS is not embedded into science teaching in Greece. To study the possibility of its integration, a PD-program for in-service science teachers was organized. All three teaching approaches we found in the literature for NOS instruction (history of science, scientific inquiry, socio-scientific issues) were used. It was decided to start with the History of Science approach so that teachers could realize that NOS is inherent to scientific knowledge. The selected historical unit was on the concept of atmospheric pressure and its development from 1638 to 1669 (Galileo's-Boyle's book publication). The concept and the period were selected because all NOS aspects, chosen as important from the consensus view adopted, are pointed out. Trainee teachers were asked to note down all NOS aspects they recognized during the narrative. By its end, an extensive discussion in the plenary took place on NOS aspects, which were finally written on a whiteboard. Teachers expressed their satisfaction with the process and mentioned that it worked metacognitively for them, since they learned a chapter of history that is not widely known, and they were impressed by the scientists' interaction at this time. Following up in the PD-program, teachers used part of this content either in a lesson plan they were assigned to organize or in classroom observations of their instruction in the next school year, to integrate NOS aspects into teaching.