The not-so-small mixing angle theta13 measured at Daya Bay, RENO, and Double Chooz,
stimulated many design activities for next-generation experiments. In this talk, I
will talk about several aspects of the physics potential in atmospheric neutrino
experiment such as ORCA and PINGU, including mass hierarchy and CP measurements.
Their physics potential can be further extended by observing neutrino trident
production with double muon tracks for direct constraint on new physics beyond the
SM, essentially turning neutrino oscillation experiment to a neutrino collider.