My astrophysics research has focused on the interstellar and intergalactic medium of our own, nearby and distant galaxies. A primary tool in this endeavour has been the 21cm line of neutral hydrogen (HI), but insight into the evolving star formation rate in galactic disks has also come from the radio continuum and infrared portions of the electromagnetic spectrum. Recent contributions have included elucidation of the interaction history (over the past 5 billion years) of one of the nearest external galaxies, Messier 31, via extremely sensitive HI imaging of its extended environment. Faint gaseous filaments, which likely have only a microscopic neutral fraction, trace the ancient interaction of Messier 31 and it’s smaller companion, Messier 33. The debris of that interaction fuels ongoing accretion onto both systems. Similar phenomena, dating from an earlier epoch of enhanced interaction, are likely the reason that a statistical excess of neutral hydrogen is found in the environment of many galaxies. This has been pursued in a recent PhD project under my supervision to detect and study comparable systems for a wide range of host galaxy masses and environmental conditions. Another research focus of the past years has been the detection and documentation of the large-scale magnetic field topology of nearby galaxy disks, a vital constituent of the cosmos that is only beginning to reveal its prevalence and importance.