The Spine project is an EU H2020 project, which develops and validates an end-to-end modular set of open source software tools for energy system modelling (the so-called Spine Toolbox). The tools enable open, practical, flexible and realistic planning of future European energy grids. The Toolbox will be suitable for both detailed modelling of complex features in energy systems as well as for large-scale problems. The Spine Toolbox provides a skeleton where tools and models can be put together in any way the user wants to. The clear-cut modularity of the tools and models within the Spine Toolbox unleashes innovation potential, as it will be possible to develop new functionality without understanding the detailed implementation of all the parts in the toolbox. This allows, for example, a large energy consumer to include a detailed model of their process within the larger energy system and seek to optimize its processes for cost-effective flexibility. Thus, Spine Toolbox can be used to test new concepts and it can lead to new products, services and business models. The Spine project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement Nr. 774629.