Abstract : Some specific effects seen in the interactions of swift hydrogenic beams penetrating thin foils are presented. We describe first dynamic effects due to periodic electron density fluctuations trailing fast charged particles moving in solids which can sustain plasmon oscillations. Studies of non equilibrated charge distribution dowstream very thim foils permit us to separate the role played by projectile and target electrons in neutral atom production. The observation of bound molecules emerging from thin target raises questions about their formation and the processes involved. Finally we show how original measurements on the dissociation of fast molecular ions by thin foils has opened up new possibilities for the investigation of molecular ion structure.