Non-Gaussian fluctuations for exploring a phase transition at the highest density in the universe

We review recent progress on the experimental search for the QCD critical point in the beam-energy scan of relativistic heavy-ion collisions. Non-Gaussian fluctuations of conserved charges are believed to be promising observables for this purpose, and active experimental and theoretical studies on these observables have been performed over the last decade. We report on the latest experimental results having a nonmonotonic behavior expected from the criticality and future experimental plans. (author)