The CLOUD collaboration is pioneering the first fundamental research reactor antineutrino experiment using the novel LiquidO technology for event-wise antimatter tagging. CLOUD’s program is the byproduct of the AntiMatter-OTech EIC/UKRI-funded project focusing on industrial reactor innovation. The experimental setup comprises an up to 10 tonne detector, filled with an opaque scintillator and crossed by a dense grid of wavelength-shifting fibres. The detector is expected to be located at EDF-Chooz’s new “ultra-near” site, 35 m from the core of one of the most powerful European nuclear plants, with minimal overburden. Detecting of order 10,000 antineutrinos daily and with a high (100) signal-to-background discrimination, CLOUD aims for the highest precision of the absolute flux, along with explorations beyond the Standard Model. Subsequent phases will exploit metal-doped opaque scintillators for further detection demonstration, including the first attempt at surface detection of solar neutrinos.