Fuente: WIPO "tomato" A method for determining the penetration properties of a compound into and/or through a plant leaf wax cuticular layer, said method comprising a) providing a model plant wax layer comprising at least one wax and Nile Red; b) subsequently contacting the model plant wax layer with a composition comprising the compound; and c) monitoring the penetration of the compound into and/or through the model plant wax layer by monitoring the change in Nile Red fluorescence. Furthermore, the use of Nile Red comprised in a wax layer for determining the penetration properties of a compound into and/or through said wax layer is described, and a wax layer deposited onto a solid support, wherein said wax layer comprises at least one plant wax and Nile Red.