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 inthe reflected light and thermal emissionregimes. 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 forthese different aspects are presented. Finally a brief account of theground based programmes and space-based projects and their potentialities forEarth-like planets is made and discussed.