In computer science methods to aid learning are very important, because abstract models are used frequently. For this conventional teaching methods do not suffice. We have developed a learning software, that helps the learner to better understand principles of compiler construction, in particular lexical analysis. The software offers on the one hand an interactive introduction to the problems of lexical analysis, in which the most important definitions and algorithms are presented in graphically appealing form. Animations show how finite automata are created from regular expressions, as well as, how finite automata work. We discuss principles used throughout the design of the software and give some preliminary results of evaluations of the software and discuss related work.