The SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) instrument aims at detecting extremely faintsources (giant extrasolar planets) in the vicinity of bright stars1. Such a challenging goal requires the use of a very-highorderperformance Adaptive Optics [AO] system feeding the scientific instruments with a quasi-perfect flat wave frontcorrected from all the atmospheric turbulence and internal defects. This AO system, called SAXO (Sphere Ao foreXoplanet Observation) is the heart of the instrument, a heart beating 1200 time per second and providing unprecedentedimage quality for a large ground based telescope at optical/near infrared wavelength. We will present the latest resultsobtained on-sky, demonstrating its exceptional performance (in terms of correction quality, stability and robustness) andtremendous potentiality for exoplanet discovery