Abstract: Tunneling between two degenerate vacua is allowed in finite-volume Quantum Field Theory. This effect induces a non-trivial vacuum energy, which results from the competition of different saddle point configurations in the partition function. In this talk, I will describe this mechanism and discuss its relevance to induce a cosmological bounce in light of singularity theorems in General Relativity. I will briefly discuss the role of anisotropies in such a model.