Keywords: inkjet printing, bubbles, drop formation, air entrainment, impact Abstract: Piezo-acoustic inkjet printing has become a mature technique for high performance printing. Nevertheless, there are still various scientific challenges. In this overview talk I will cover some of them: (i) Coupling between the fluid dynamics and the acoustics, in particular when a disturbing bubble has been entrained in the ink channel. (ii) Optical and acoustical monitoring of the bubble. (iii) Mechanisms of the bubble entrainment. (iv) Droplet formation and pinch-off of droplets. (v) Droplet impact on substrates. Main further contributors to the research: Jos de Jong, Roger Jeurissen, Arjan van der Bos, Michel Versluis, and the colleagues from Oce Technologies: Hans Reinten, Herman Wijshoff, and Marc van der Berg.