It is very important to assess cell confluency, precipitate size and transfection efficiency in the Cell Factory under magnification. However, because ten tray cell factories (abbreviated henceforth as 10TCF) are not easily visualized under magnification, we have incorporated a one tray Cell Factory (1TCF) as an observation control. It should be noted a highly efficient transfection will cause 60–80% cell detachment at time of harvest. For this reason, it is critical to process both culture media and cell pellet.