Photonic circuits are regarded as a potential route for breaking the speed limitation of electronic circuits. For the miniaturization of photonic chips, the width of the cladding separating the optical waveguides should be minimized. By designing pure dielectric structures with spatial dispersions, we recently unveiled an approach to reduce the width of cladding directly to zero (Read more), without leading to crosstalk between the neighboring waveguides. This breakthrough overturns the long-held tenet that cladding is necessary for optical waveguiding.