Our results on the first transient dipolar interaction in a dense atomic cloud in a thin vapor cell are now in Physical Review Letters. There we control the density of the thermal cloud on a fast timescale (~ ns) using a method called LIAD, i.e. light-induced atomic desorption, and increase it till there is more than one atom per reduced wavelength. That increases the coherent-coherent atom interaction hence causing a lineshift, a property that we measured in the transmitted signal with a single-photon detector resolution. Such a fast density tunability will be a key contributor to a hybrid atom-photonics platform for photon routing, switching, and large nonlinearity useful for quantum information processing.