Computer tools can support and accelerate the development and implementation of first-principle models for chemical and biological processes significantly. Several application examples illustrate this in the contribution. Models of a biochemical reaction network, of a catalytic fixed bed reactor, and of two chemical production processes are considered. The models are implemented in a structured way in the process modeling tool PROMOT, whose key features are discussed. The structuring of the models is based on a uniform structuring methodology whose main ideas are presented as well.