A leitmotif in the evolution of programming paradigms has been the level and extent of parametrisation that is facilitated — the so-called genericity of the paradigm. The sorts of parameters that can be envisaged in a programming language range from simple values, like integers and floating-point numbers, through structured values, types and classes, to kinds (the type of types and/or classes). Datatype-generic programming is about parametrising programs by the structure of the data that they manipulate, exploiting that structure when it is relevant and ignoring it when it is not. Programming languages most commonly used at the present time do not provide effective mechanisms for documenting and implementing datatype genericity. This volume is a contribution towards improving the state of the art.