We propose to use new European astronomical facilities in conjunction with the power of massive galaxy clusters used as gravitational telescopes in order to explore the question of galaxy formation and evolution. In particular, new spectroimagers such as the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope and the Atacama Large Millimetre Array (ALMA) allow to directly access and resolve the physical information inside distant galaxies on a pixel-to-pixel basis.The first part of the project will make use of MUSE to study the distribution, size, kinematics and physical properties of very distant galaxies (in particular at z>3), and the addition of gravitational lensing will bring these observations down to very faint luminosities.The second part of the project will characterize the multiwavelength properties of distant (z>1) galaxies, from optical to radio wavelengths, including a millimetre follow-up with ALMA. Only with the gravitational magnification in strongly lensed arcs will ALMA be able to already resolve different parts of high redshift galaxies during the Early Science phase.FInally, we will develop a dedicated software, called 3DLENS, in order to reconstruct the intrinsic properties of lensed sources observed with any spectroimager such as MUSE or ALMA.The proposed integration period will ensure that the researcher, who has just been hired as a tenure-track asssistant astronomer position, will access tenure position quickly in the institute. It will benefit his career as well as the scientific outcome of the European facilities mentioned.