Multi-critical point principle (MPP) is an interesting theoretical possibility, which claims that coupling constants of low energy effective theory are tuned to the point where the vacuum structure or history of the Universe changes drastically. In this talk, I will try to explain the basic concepts and ideas of the MPP without going into the details of underlying physics. Then, I will present a few phenomenological applications of this principle, including our recent works (arXiv:2107.10720 and paper in preparation).