Transmission Electron Microscopy (TEM) in-situ straining and High Resolution Transmission Electron Microscopy (HRTEM) experiments are performed to study the nanoscale precipitation and the overcoming mechanisms of precipitates by moving dislocations in 6056-T6 aluminium alloy. The direct observation of dislocations pinned on precipitates under the effect of the applied stress allows to determine the real distance between precipitates along the dislocation lines. This is one of the most relevant microscopic parameter for modelling precipitation hardening. This parameter is a function of the shape, the dimensions and the density of precipitates.