Molecules in Action: Extragalactic ISM at high resolution

During the last two decade, observations have shown the potential of molecular tracers to get insights into the physical processes taking place in the central regions of active galaxies. However, observations were severely limited by both sensitivity and resolution. This resulted also in a limited sample of bright enough galaxies where molecular species other than carbon monoxide could be observed. Current instruments like ALMA and the upcoming NOEMA are already changing our view of the extragalactic ISM molecular observations. In fact, it is now possible to study the physical properties of individual spatially resolved star forming GMCs in external galaxies, as well as resolving the physical structure of the ISM in the surroundings of AGNs at scales of a few parsecs. Here I quickly review some of the most recent observational studies in the nuclear regions of galaxies which are setting new standards in the ways we can study the extragalactic ISM properties.