Now that we've found the Higgs Boson particle, what do we look for? The Higgs is important, sure, but there is a lot in the universe we don't know about. For example, gravity is one of four forces in the universe (gravity, electromagnetic, weak nuclear, strong nuclear) and it is by far the weakest force. Yet, gravity keeps all the planets together, keeps us on the ground, and affects everything. One of the explanations might be extra dimensions. For example, more than just the three dimensions we live in.
it's complicated, but this video explains it nicely. It's an illustrated conversation between very smart people discussing the seminal question, "What's next?" via YouTube