Generalised (or unintegrated) parton distributions (GPDs) allow for a unified description of hadron structure as they encompass standard parton distributions and nucleon form factors as forward limits and integrals, respectively, and go beyond projections of nucleon structure by providing also information about the correlation of the different degrees of freedom. These new functions offer opportunities to study a uniquely new aspect of nucleon structure: the localisation of partons in the plane transverse to the motion of the nucleon and correlated with their longitudinal momentum. As such they provide a nucleon tomography (analogous to CT scans in medical imaging). The ability to describe longitudinal momentum distributions at a fixed transverse localisation is a prerequisite for studying the so-
GPDs are studied in hard exclusive reactions, where the nucleon stays intact and the final state is fully observed. The most prominent processes are deeply virtual Compton scattering and deeply virtual meson production. While the former can be most cleanly interpreted in terms of GPDs, the latter provides also flavour dependent information. Both processes will be studied intensively Jefferson Lab at 12 GeV.periments.