This talk explores the multifaceted role of neutrinos in astroparticle physics. Firstly, we look at understanding the fundamental properties of neutrinos. Secondly, we explore how neutrinos serve as probes for cosmic objects, while further revealing their intrinsic properties. Finally, we study neutrinos as probes of cosmic populations, including dark matter and relic neutrinos, alongside their role in probing cosmic objects and advancing our understanding of neutrino properties. We will also discuss how to extend beyond IceCube through second generation neutrino experiments such as Gen2 and P-ONE via sub-nanosecond photosensor technology.