A bioreactor is a device simulating physiological environments for different biotechnological applications. In highly promising research fields like tissue engineering microsized bioreactors were utilized successfully promoting mammalian cells to grow and build 3D cell structures similar to in vivo environments. For any practical application and even for improved R&D it is necessary to generate and maintain a physiological environment over the whole cultivation period (hours, days or weeks, in case of artificial organs even up to months). Depending on the field of application physiological environments can comprise different parameters. In case of mammalian cell lines these parameters require a complex supply and monitoring system. Thus, we developed a semi-automated bioreactor-system for long-term cultivation of different mammalian cell types imitating physiological conditions. The system included detection and control of the following parameters: temperature, pH-value, gas concentration and the continuous supply with nutrients. A micro fluidic network was established enabling a high through-put cultivating system as bioreactor-system. The bioreactor-system consists of several micro-sized chambers in a microliter scale (the related article discussing the micro-sized chambers “Miniaturized Flow-Through Bioreactor for Processing and Testing in Pharmacology” by Boehme et al is published within this issue). The chambers were placed in a polymeric slide each with an individual medium supply and disposal. Every single chamber thus was connected to an individual syringe-based micro-pump setup and supplied by nutrients solution with a velocity of 100μl/h. The pH-value was observed optically and controlled via CO2 supply. All gas interchanges into every single chamber were realized via semi permeable membranes. The required temperature was adjusted via an appropriate custom-fit heating system utilizing MOSFETs allocated on an aluminum board along the slides. Two slides each were housed in a PMMA case. This bioreactor-system is a first prototype for larger systems aiming for the parallel operation of up to 100 micro-sized reaction chambers. © 2017 Trans Tech Publications, Switzerland.