Instrumental control of processes in the chemical and petroleum industries has been going on for some 50 years, but for much of that time the technique involved only single-function instruments that measured temperature, pressure or flow and actuated simple control mechanisms. By 1945 a number of people began to realize that this type of control was crude compared to what could be done using instrumentation that would continuously analyze a process stream and provide detailed information on its composition. These men, largely within the R and D areas of large industrial concerns, gathered groups around them capable of developing such powerful process instruments. These groups contained hybrid elements - physicists, mechanical engineers, electrical engineers and chemists - whose pooled skills created the analytical tools. Many of these instrumental creations, proven and improved in process applications, are now produced by instrument companies.