Current small-scale cosmological controversies are coming down to the precision level of observations. The key point is whether a better understanding of baryonic physics, dark matter physics, or both is required to address these challenges. In this talk, I will describe how very long baseline interferometric observations of extended AGN jets (sometimes gravitationally lensed) are contributing to understanding some of these small-scale cosmological issues while simultaneously providing insights on the jet physics up to the earliest epochs (z>6).