Learn how to make the invisible visible in a laboratory of hemodynamics

This essay documents the practical activity consisting in seeing and learning to see the invisibility of the heart ramifications within an hemodynamic laboratory exploiting imaging technologies. The ethnographic observation shows that the visibility of the images is socially constructed and negotiated among laboratory members and involves the use of heterogeneous artefacts and multimodal semiotic resources. Their professional vision is social, dynamic, situated and implies the mastery of a practical, tacit and body knowledge. The ethnographer herself, like a novice, learns step by step to see what was for her initially invisible and confused, by succeeding to notice the pertinent elements - progressively standing out on the screen's background- for the purpose of activities, while some practitioners perform the role of instructors guiding her through gesture, words and gazes, in the vision of these elements.