In the vast universe full of diversity, galaxies also come in multiple shapes, sizes and colours. Galaxies contain stars, an interstellar gaseous medium (ISM), and dark matter. The neutral (atomic and molecular) hydrogen gas discs are the pivotal components of the cold ISM in galaxies, and are the fuel for star formation (see right figure). These gas discs are also excellent tracers of diverse astrophysical processes that are at play in the cosmic neighbourhood of galaxies. The main goal of my research is to investigate the influences of the cosmic environment on the evolution of galaxies by observing the characteristics of their atomic and molecular gas discs located in different environments.