Description Today scientists and engineers are commonly faced with the challenge of modelling, predicting and controlling multiscale systems which cross scientific disciplines and where several processes acting at different scales coexist and interact. Such multidisciplinary multiscale models, when simulated in three dimensions, require large scale or even extreme scale computing capabilities. Progress in science and technology is limited by our ability to solve efficiently such problems on available distributed computing infrastructures. The MAPPER project will respond to this critical need by developing computational strategies, software and services for distributed multiscale simulations across disciplines, exploiting existing and evolving European e-Infrastructure. Driven by seven challenging applications from five representative scientific domains (fusion, clinical decision making, systems biology, nano science, engineering), MAPPER will deploy a computational science environment for distributed multiscale computing on and across European e-infrastructures. By taking advantage of existing software and services, as delivered by EU and national projects, MAPPER will result in high quality components for today’s e-Infrastructures. We will advance the state-of-the-art in high performance computing on European e-Infrastructures by enabling distributed execution of multiscale models. We will develop tools, software and services that allow two modes (loosely - and tightly coupled) of multiscale computing, in a user friendly and transparent way. We will integrate our applications into the MAPPER environment, and we will demonstrate their enhanced capabilities by answering one challenging scientific question related to each application. We plan to collaborate with other projects on adaptation of successful MAPPER methodologies, and will work with resource providers to develop policies facilitating the new multiscale computing paradigms.