As far as I understand, the latest calculations say that wormholes do not exist. Nonetheless, as a theoretical construction, they would be a "bridge" between two non-contiguous portions of spacetime. At first I thought they might just be a discontinuity in spacetime, but then I read of the metric defined "inside" them. Since they are described as a bridge between two parts of spacetime, any "inside" would be by definition not part of spacetime, which seems odd if a spatiotemporal object (an electron, whatever) could exist in it. So what would they be "made" of, if not spacetime? If they are part of spacetime, then they no longer fit the description of "bridge". Help!