A comprehensive view of the CGM/IGM with background sources

The circum-galactic medium (CGM) and inter-galactic medium (IGM) contain the vast majority of the baryons, and are difficult to observe directly due to their very low densities. However, the CGM and IGM are well detected with background sources, such as bright quasars. Quasars give us a wealth of information on the gas properties and in some circumstances, these properties can be put in relation to the host galaxies. Today, we are entering a new era with a large number of surveys being conducted with large-field IFUs (MUSE, KCWI) and large multi-object spectrographs (4MOST, WEAVE-QSO, DESI, etc.). This workshop comes at a critical time, where large MUSE programs are being wrapped up (supported by ANRs) and new observational campaigns are starting using the IGM as a cosmological tool. The aim of this workshop is to bring together experts in observations along with theorists to discuss the latest discoveries and to foster new synergies among the various experts around the new upcoming surveys.