Three-dimensional (3D) culture systems provide cell–cell and cell–extracellular interactions that reproduce the cellular microenvironment in vivo better than typical two-dimensional monolayers. This property is of paramount importance in many applications, including disease modeling, drug toxicity assessment, and manufacturing of stem-cell–based products (1). Cultivation in stirred-tank bioreactors using perfusion mode opens up new possibilities in the cultivation of 3D cell aggregates. Perfusion allows for removal of detrimental metabolites, cell debris, and proteases from the culture as well as the addition of…