Simply put, a bioreactor is a stand-alone cell culture vessel enabled with sensors. Bioreactors differ fundamentally from traditional R&D cell culture in their ability to monitor and control key parameters such as temperature, pH, and dissolved oxygen (DO). Continuous, in situ monitoring of these parameters allow for a deep understanding of the growth environment of a given cell population -- creating avenues for process improvement. Paired controls enable dynamic, real-time responses as cells grow and the culture changes over time. With these capabilities, bioreactors can overcome limitations of traditional cell culture enabling the use of cell culture for commercial or clinical purposes.