New concepts for high energy colliders.

High energy colliders are essential instruments for investigation of fundamental physics. Recent results from the LHC point to the existence of a standard-model-like Higgs boson, while the scale of new physics is being pushed toward and beyond the TeV scale. Such a scenario requires very precise measurements of the Higgs boson with the entire standard model sector as well as colliders able to explore the multi TeV scale. Design studies for high luminosity e+e- colliders for H, Z, W and top factories are underway. At the same time, projects for order of hundreds TeV pp colliders are on-going, hosted in the same tunnel infrastructure. New concepts with the capability of studying the same physics program and with the possibility to extend the energy reach are emerging. The low emittance muon collider proposed by the INFN provides unprecedented high energy reach. At the same time, the research program for extreme gradients acceleration based on plasma wake-fields is continuously growing. A review on the accelerator program toward the exploration of high energy physics will be given covering both the baseline programs and the new concepts.