Scientists at Tokyo Institute of Technology approach the two decade-old mystery of why an anomalous metallic state appears in the superconductor-insulator transition in 2D superconductors. Through experimental measurements of a thermoelectric effect, they found that the "quantum liquid state" of quantum vortices causes the anomalous metallic state. The results clarify the nature of the transition and could help in the design of superconducting devices for quantum computers.