Volume 1 includes the papers of the three-day technical conference having taken place in the course of the Session (June 17-19, 2019). It is subdivided into two parts and contains, beside general information regarding CIE, on 1 858 pages the full papers of the oral presentations, presented posters and posters presented at the conference. Volume 1 is already available from the CIE Webshop or from the National Committees of the CIE. Volume 2 contains official reports of the administrative and technical meetings of the Session, thus presenting an overview on the technical work in CIE achieved during the last Quadrennium. It will be provided in due course and will be freely available on the CIE Website. [more]