The functional analysis of grinding tools, and especially use-wear analyses developped in the last decade, aims at reconstituting their working order and the nature of the matters transformed. Our paper discusses how a phytolith analysis on querns active surface can bring information on Neolithic dietary habits and grinding techniques. Through the example of two Early Neolithic series of the northern half of France (Berry-au-Bac "Le Vieux Tordoir" et Loison-sous-Lens), we discuss the interest and limits of this method to approach the function of querns under temperate climate.