Our modern standard of living depends strongly on the industrial process industry. The raw materials used to make consumer products are produced in complicated chemical reactions that are difficult to control. In order to increase efficiency and reduce waste, new process control schemes are needed. In recent years tomographic methods have been developed to see inside industrial chemical processes. The sensing mechanisms used in process tomography include electrical measurements (current, capacitance, or inductance) and absorption of various forms of energy. This data can be reconstructed to form cross-sectional images of the material in the process vessel, as demonstrated in three examples: Optical tomography is used to monitor the fuel spray pattern in internal combustion engines and to develop more efficient designs. Electrical resistance tomography has been used to study polymerization of nylon and to provide environmental monitoring at liquid storage facilities. These examples show that process tomography can help industry to protect the environment.