Generally, a digital twin is a software-model as a prototype for some product, ordered by a customer. It shell be used on all stages of industrial production of this ordered product, compering the actual state with the model und correcting the differences. A "virtual world" will be created from the "real word" and both "worlds" communicate with each other during production. At the educational institutions of engineering like universities, trainings centres or schools the digital twins are software-models of industrial plants, which are simulated and visualized like its industrial originals and synchronized with them. The actual paper, which short edition was presented by Zacher (2020), shows steps of design of digital twins upon some examples of the bachelor's and master's degree program at the Universities of Applied Sciences Darmstadt, RheinMain, and the Baden-Wuerttemberg Cooperative University (DHBW) Stuttgart. It will be described why and how it is possible to use the digital twins. The ways from an original device to its model will be drawn. The different stages of the development of software-models, which are equipped with different levels of source code, will be shown. The actual trends to include the hardware into a software-model, so called hardware-in-the-loop and rapid control prototyping, will be described. Finally, the advantages and disadvantages of digital twins for engineering study including the economic considerations will be discussed.