Abstract: A microfermentor device that can be used for a wide variety of purposes is described. The microfermentor device includes one or more cell growth chambers having a volume of less than 1 ml. The microfermentor device can be used to grow cells used for the production of useful compounds, e.g., therapeutic proteins, antibodies or small molecule drugs. The microfermentor device can also be used in various high-throughput screening assays. For example, the microfermentor device can be used to screen compounds to assess their effect on cell growth and/or a normal or abnormal biological function of a cell and/or their effect on the expression of a protein expressed by the cell. The device can also be used to investigate the effect of various environmental factors on cell growth, biological function or production of a cell product. The device, including various controlling components and sensing components can be microfabricated on a support material.