We explored a novel approach to directly visualize THz surface polariton propagation in both space and time – accessing the polariton’s group and phase velocities, as well as its damping. Through photoexcitation, we even achieved subcycle control of the polariton propagation.The results obtained in close collaboration with the group of Miriam Vitiello in Pisa (NEST, CNR) and Eva A. A. Pogna in Milano (CNR-IFN) have been published in Nano Letters (external link, opens in a new window) (Coverstory) (external link, opens in a new window).