Clinical translation of engineered tissues into regenerative medicine applications, and the effort to reduce the use of animals for the screening of drugs and other compounds, result in an increasing demand for human tissues engineered in vitro for implantation, in vitro screening systems and basic research. Further development and optimization of in vitro models for quantitative studies of biophysical stimulation and mass transport in engineered tissues is seen as one of the high research priorities. A recent international symposium held in The Netherlands discussed the state of the art and key challenges in the development of bioreactor platforms and microscale technologies. Here we summarize the current status and future development of in vitro tissue models, based on the findings presented at this symposium.