A review of the state-of-the-art in object-oriented modelling of virtual-labs for control education is presented. The presentation emphasizes the main advantage of this methodology: the reduction in the modelling effort. The combined use of different languages and tools is addressed: Modelica/Dymola, Sysquake, Easy Java Simulations (Ejs) and Matlab/Simulink. In particular, three approaches to virtual-lab implementation are discussed. The Modelica language is used in all of them for describing the model and Dymola is used for translating the model into executable code. For the first approach, the user-to-model interactive interface (i.e., the virtual-lab view) is built using Sysquake. Next approach consists in implementing the virtual-lab view with Ejs, and using Matlab/Simulink as an interface between the model and the view of the virtual-lab. Finally, a procedure for describing the complete virtual-lab using the Modelica language and Dymola is discussed. The proposed approaches are illustrated by means of several virtual-labs for process control education.