Until recent years knowledge of chemical processing was descriptive and qualitative.

In 1810 modern chemical theory was born and process description became quantitative.

Then about 1900 the quantitative engineering approach was developed, first for physical changes, called the Unit Operations, and somewhat later for chemical operations. This we call the American approach.

In 1957 European chemical engineers brought together the design of chemical and their related physical operations under the name of Chemical Reaction Engineering, or CRE. This approach and name received practically universal acceptance.

Today the methods of CRE are widely used in the processing of biochemical and all sorts of other systems,

This talk wanders through this development.