MEMPHYS is a proposed $0.5$ Mton scale water Čerenkov experiment to be performed deep underground. Possible sites are under study in the European FP$7$ design study LAGUNA. It is dedicated to nucleon decay, neutrinos from supernov\ae, solar and atmospheric neutrinos, as well as neutrinos from a future Super-Beam or $\beta$-Beam. Its performance with neutrino beams includes the possibility of measuring the mixing angle $\theta_13$, the CP-violating phase $\delta$ and the mass hierarchy. One R$\&$D item currently being carried out is MEMPHYNO, a small-scale prototype with the main purpose of serving as a test bench for new photodetection and data acquisition solutions, such as grouped readout system. We review here the MEMPHYS physics reach and present the status of the MEMPHYNO prototype.