Theorema 2.0: A System for Mathematical Theory Exploration Theorema 2.0 stands for a re-design including a complete re-implementation of the Theorema system, which was originally designed, developed, and implemented by Bruno Buchberger and his Theorema group at RISC. In this talk, we want to present the current status of the new implementation. The emphasis of this presentation is on the user interface of the system, i.e. how a user is supposed to get her jobs done supported by the Theorema system. Topics range from formula input over structuring and administration of bigger knowledge bases, knowledge archives, automated proving, interactive proving, customization of automated proving methods, generation of readable proofs until tool support for navigating through large structured proofs. Theorema 2.0 is - like its predecessor versions - based on Mathematica, which means that it is implemented in the Mathematica programming language and that it uses the Mathematica notebook frontend as its user interface. Unlike the command-oriented interaction pattern typically propagated in Mathematica applications, Theorema 2.0 is heavily based on the graphical user interface capabilities supported in recent versions of Mathematica. As a result, the user needs the keyboard only for typing the mathematics (definitions, theorems, explanatory text) into the system, all actions to be performed are guided by the graphical user interface. Following this approach, the difference between writing a Theorema document and writing a "standard mathematical document" shrinks to almost zero. Moreover, the learning curve for using a mathematical assistant system is considerably flattened and the system will be more attractive, in particular for beginners. Theorema 2.0 runs on all platforms, on which Mathematica is available. Mathematica is needed to run the system, but the Theorema system itself is open source licensed under GPL and is available at GitHub. The talk is intended as a live system demo and should serve as an introductory course for other workshop presentations related to the Theorema system.