The physical bases of the detection and characterisation of extrasolar are reviewed and the first findings are presented. A special attention is paid to the imaging method in the reflected light and thermal emission regimes. They both have their advantages and disadvantages, including artefacts, in the determination of planet physical parameters (mass, size, albedo, surface and atmospheric conditions etc.). New perspectives for these different aspects are presented. Finally a brief account of the ground based programmes and space-based projects and their potentialities for Earth-like planets is made and discussed.