The Neolithic period Chassey culture in southern France from 4200 to 3500 Cal. BC developed a specialized lithic technology for flint bladelets that used a heating process as an essential part of the production. Experimental archaeology demonstrated that the heating should take place at low temperature somewhere around 250°C. To identify and quantify the physical transformations of flint at low temperature, laboratory and synchrotron experiences have been carried out on a set of heated Barremo-Bedoulian flint samples. According to our measurements, this flint consists of a nanocrystalline matrix of quartz and moganite. Evolution of mesoporous structure was observed during heat treatment. The flint transformed between 200-300°C, resulting in a reduction in the size and volume of porosity. The densification of flint is linked to changes on the nanocrystalline grain boundaries, and it is thought to have a direct impact on the improved mechanical properties from the Chassey culture lithic productions.