My general research interest ranges from cosmology, general relativity and particle physics to climate physics and meteorology. In my bachelor thesis, I investigate the production of sizable gravitational waves originating from 1st-order phase transitions in the early universe. More precisely, we consider the classical conformal (B-L) -extension of the Standard Model in which the (B-L)-number is being promoted to a new gauge symmetry that can be spontaneously broken at finite temperature. Gravitational waves can then arise from bubble nucleation and their collisions.