*Snacks and drinks at 4 pm*
Realizing efficient many-body quantum simulators requires an exquisite control over the coherence and the interactions between many particles. Rydberg atoms are emerging as a strong candidate for achieving the coherent control of large interacting systems. However recently there has been concerns due to the observation of giant inhomogeneous dephasing in large ensembles. Hence the current difficulties encountered for realizing Rydberg dressing for atomic ensembles of 100 atoms or more. In this talk I will review experimental evidences pointing toward an avalanche-like onset of off-diagonal dipole-exchange interactions, fueled by blackbody transitions. Using several time-resolved spectroscopic methods in a neatly controlled ensemble of ultracold Rydberg atoms held in a 3D optical lattice, I will present data looking into the dynamical description of this highly-correlated, many-body avalanche dephasing process. Possible ways to mitigate the decoherence will be presented.