The inner tracking system (ITS2) of the ALICE experiment is foreseen to be upgraded during the Long Shutdown 3 of the Large Hadron Collider (LHC). First data are expected to be taken during Run 4 with the upgraded High-Luminosity LHC. The planned ITS3 detector will be based on stitched, wafer-scale Monolithic Active Pixel Sensors (MAPS), bent to radii of 18, 24, and 30 mm
and fabricated on 300 mm wafers in a 65 nm CMOS Imaging technology. They will be thinned down to below 50 μm and held in place by carbon foam spacers, resulting in an unprecedented
material budget of O(0.05%) 𝑋/𝑋0 per layer. This contribution will present the detector concept, summarise the results of the R&D program, including most recent 65 nm prototypes, and provide an outlook on the path towards the final sensor development.