The origin of the asymmetry between matter and anti-matter of the Universe remains one of the most important open questions in particle physics and cosmology. We propose a novel mechanism, the lepto-bubbles mechanism, to dynamically generate this observed asymmetry. The particle that undergoes the phase transition is a SM-singlet scalar which couples to the lepton number violating Weinberg dimension-5 operator. During the phase transition, the coupling of the Weinberg operator is time-dependent, and the lepton asymmetry is generated by the interference of the Weinberg operator at different times. We calculate the lepton asymmetry produced by the phase transition using the closed time path formalism.