Atomic ISM in galaxies, near and far: Results & Surprises

The interstellar medium (ISM), from which the new stars are born and to which the old stars inject matter and energy, thereby enriching it, is indeed an integral and important component of the galaxies. Understanding the structure and evolution of the interstellar medium, that involves a diverse range of phenomena and a wide range of scales, is an interesting exercise. Radio frequency observations of the atomic hydrogen 21cm transition is a very powerful tool to study a wide range of ISM phenomenon from the Milky Way, nearby galaxies as well as over cosmological distance and timescale. I will briefly present how 21cm observations and simulation can be utilized to explore a plethora of science cases - from the local ISM conditions to galactic dynamics and all the way to the cosmic evolution of the baryons. I will particularly focus on three closely related aspects - the multiphase nature of the atomic ISM, interstellar turbulence and magnetic field - that play crucial roles in shaping the properties of the ISM. In this talk, I will explore these topics, highlighting the latest insights and challenges in our understanding of the interstellar medium.