What lies within CERN's entrails? What is the path followed by the particles that are accelerated before they collide? What does the ATLAS detector look like? Does research at CERN find applications in everyday life? From the accelerator control room to the huge Computing Centre, via the auditorium where the discovery of the Higgs boson was announced in July 2012, I invite you to experience for one day an immersion in the world of research in particle physics! Discovering emblematic installations at CERN, walking through the places where people spend every working day, meeting with researchers in various fields, descending into the ATLAS cavern ... Our visit, whose path will mimic that of the particles during their journey, will be full of anecdotes and surprises. Follow me for a guided tour of CERN, the largest scientific collaboration in the world!