The last decade has shown significant progress in understanding the impact of the cellular environment on culture physiology and its subsequent impact on productivity, product quality and downstream processes.  The FDA publication of the Process Analytical Technology (PAT) encouraged the design and optimization of at-line and on-line sensing or analytical technologies as well as autosampling systems that along with design of experiments (DOE), chemometrics, information technology and multivariate analysis allow scientists and researchers to assess the quality of the product.  The ability to measure process data real time using PAT tools, i.e. sensor technologies, data analysis and process understanding would enable manufacturing flexibility, efficiency and potentially decrease real time release.   This presentation reviews developments in sampling and sensor technologies for monitoring fermentations and mammalian cell culture in the last decade.  New technologies will be discussed as well as advances in existing technologies.  Each one of these technologies contributes to enabling PAT and increasing process understanding.