Dark Energy is probably the main discovery and the main problem in physics in the last decade. It can be due to false vacuum, self-interacting vector fields, GR violations, back-reaction to the rise of inhomogeneities or to still more unconventional physics. To select among these options fresh data are needed. After briefly discussing the above options, an outline of the DUNE-EUCLID experiment, based on tomographic lensing measurements, and aiming to study DE properties, will be presented.