Several studies have demonstrated that certain particular plants increase biodegradation of a number of exogenous organic molecules in contaminated soils. However, information on mechanisms, stages and the role of plants, direct or even indirect, in transforming such compounds is scarce. The objective of this work is to put on view phytoremediation as a technological helpful alternative for cleaning contaminated soils. General mechanisms and particular stages that plants use, as well as the complex interactions plants-native microorganisms-xenobiotics in the soil are reviewed. This knowledge will allow proposing solutions to problems of contamination and eventually recovering sites and soils.