Explore open problems in particle physics in this third lecture of a four-part series delivered by Ricardo Matheus from IFT-UNESP, Brazil. Delve into cutting-edge topics and unresolved questions at the forefront of particle physics research during this 1-hour and 18-minute presentation. Part of the Perimeter-SAIFR Journeys into Theoretical Physics program held from July 17-23, 2023, this talk offers valuable insights for those interested in the current challenges and future directions of particle physics research.