Liquid drops hitting solid surfaces deform substantially under the influence of the ambient air that needs to be squeezed out before the liquid actually touches the solid. Nanometer- and microsecond-resolved dual wavelength interferometry reveals a complex evolution of the interface between the drop and the gas layer underneath. For intermediate impact speeds (We∼1…10) the layer thickness can develop one or two local minima-reproduced in numerical calculations-that eventually lead to the nucleation of solid-liquid contact at a We-dependent radial position, from a film thickness >200 nm. Solid-liquid contact spreads at a speed involving capillarity, liquid viscosity and inertia.