Sourcetrail is a free software which can help to understand LibreOffice classes and other products. Sourcetrail allows to graphically display Libreoffice classes in a more dynamically way than Doxygen. Coupled with Vscode, navigate easily in the LibreOffice code. (beginner level). Demonstration and use case. We try to identify classes and functions involved in a bug. This conference is specially for beginners. (probably boring for experienced developper). At the end of conference, you will be able to use Sourcetrail.