Scientists from a wide range of disciplines have been mobilized in parallel with the formidable restoration work being carried out on Notre-Dame Cathedral following the dramatic fire of April 16, 2019. In particular, the CNRS and the French Ministry of Culture have joined forces with the Établissement Public chargé de la conservation et de la restauration de la cathédrale Notre-Dame de Paris to support a number of expert appraisal and research initiatives. After a first part recalling the consequences of the fire and the challenges of restoring Notre-Dame, the conference will review, through a few examples, the various research projects linked to the cathedral. These concern not only restoration issues, but also an understanding of the cathedral from a historical point of view, particularly in medieval times (dating of construction phases, materials and techniques used by medieval builders, supply circuits, climate).