The physical outcome of the LHC is not foreseeable yet. But in any physics case, the next collider will be a linear electron - positron accelerator. To realize such a machine, a global effort towards high gradient superconducting cavities is on its way. Big achievements on this topic were done already, but still we have a lot to learn and the R&D continues. A total amount of 16000 cavities with an average gradient of 31.5 MV/m are needed to realize the ILC, where this goal is a worthy challenge. An introduction into superconducting cavities will be given and the struggle on the way to built the next collider will be described.