Understanding soil evolution requires characterising, quantifying, and modelling the major processes that govern pedogenesis. We proposed to study one of the most widespread processes in soils: lessivage, understood as the vertical transfer of fine particles from a horizon, called eluviated, to another horizon, called illuviated. Lessivage fluxes were never measured to our knowledge due to obvious technical difficulties. In addition, despite its description in many soil types, the existence of this process is somewhat controversial. We designed a laboratory experimental device to imitate the lessivage process and to test the impact i) of extreme events, as heavy rain, and ii) of the structure of the eluviated horizon on lessivage. We used a rainfall generator that allows the examination of the effect of rainfall on soil under controlled conditions. Two climatic modalities were tested: heavy rain on dry soil and small intensity rainfalls on wet soil. We present here the first results of these experiments.