LEWIS is a large program, approved in the ESO period 108, to obtain the first homogeneous integral-field spectroscopic survey of ultra-diffuse galaxies (UDGs) in the Hydra I cluster of galaxies with MUSE@ESO-VLT. The new sample of 32 UDG candidates have been recently discovered inside 0.6 virial radius of the cluster. UDGs are empirically defined to be faint (μ0,g ≥ 24 mag/arcsec^2) and diffuse (Re ≥ 1.5 kpc) objects, with stellar masses similar to dwarf galaxies. For all UDGs in Hydra I, the MUSE data will confirm the cluster membership, measure their stellar kinematics and stellar populations. In this talk I would like to review the main results for the LSB galaxy population in Hydra, including UDGs, and the preliminary results obtanied by the spectroscopic follow-up data obtained with LEWIS.