Plant cell and tissue cultures represent a suitable alternative as production systems for valuable plant secondary metabolites. Unlike traditional extraction from agricultural grown plants, the active ingredient production in biotechnological processes with in vitro cultures takes place in closed bioreactors under controlled conditions. This allows a year-round production with constant quality and quantity. However, the development of biotechnological processes with plant in vitro cultures is often time-consuming and requires parallelized screening systems. Furthermore, the design, optimization, and control of economic processes presuppose knowledge about the physiological state of the biological system and the kinetic parameters of biomass and product formation. To gain access to these data, suitable process-monitoring methods are required which provide information about the physiology of the process, both on a macroscopic and on the single cell level. However, due to the morphology of plant cell and tissue cultures, many methods for bioprocess monitoring that are used for mammalian and microbial cultures are not applicable. This chapter covers methods that are appropriate for monitoring of biotechnological processes with plant cell and tissue cultures: The conductivity of the growth medium is a powerful parameter to estimate the growth of complex plant cell aggregates and tissue structures. The next section describes the application of the RAMOS – a small scale cultivation system – for heterotrophic and phototrophic plant cell and tissue cultures. Flow cytometry is a tool to obtain segregated data of bioprocesses. Further, we describe a novel approach of cell immobilization for physiological studies and the design of bioprocesses, the 3D Green Bioprinting.