This concluding chapter recaps what has been learnt in the previous chapters about the Standard Model. This model is highly successful in describing particle physics phenomena. Some of its successes are briefly underlined, such as the number of light neutrino families. However, as with any model, it also has its weaknesses, which are also provided. The most important open questions of particle physics are addressed in the second part of the chapter, in particular, the matter–antimatter asymmetry, the hypothetical presence of the dark matter. Possible extensions of the Standard Model are presented to incorporate massive neutrinos.