Most developers have been to the situation where they encountered a legacy and very threatening code, with a lot of unknown functionality, and they don't know from where to start. Usually this is not a very pleasant task. In my talk I would like to explain the methodologies of refactoring a legacy code and what is the best and efficient way to do it, without breaking the functionality of the system. I will explain from where to start, how to do it carefully, how to use existing tests and which tests it is important to write. Hopefully, after this session you will fell more comfortable and confident to take those tasks !