Résumé
The 'Hubble tension' is a ∼ 5σ discrepancy-in the ΛCDM context-between the H0value derived from early-and late-universe observations. I discuss guidelines toresolving this long-standing mystery, arguing that our best shot is throughmodification of the pre-recombination physics, right around matter-radiationequality. I introduce a toy model dubbed 'Early Dark Energy' (EDE) in which afrozen scalar-field contributing a fraction fEDE(zc) ∼ 10% of the energy densityof the universe around zc 3500 and diluting as or faster than radiationafterwards can accomodate CMB, Baryon Acoustic Oscillation (BAO), growthfunction (FS), Supernova Ia (SNIa) and the latest SH0ES measurement of H0. Idiscuss some potential challenges that this model is facing in light of thelatest weak lensing surveys, but argue that the level of tension between weaklensing surveys and Planck within ΛCDM does not allow to make robust conclusionsabout the status of EDE. Future CMB and LSS measurements will provide adefinitive test to this scenario.