Transitional Millisecond Pulsars

Millisecond pulsars in tight binaries have recently challenged our understanding of physical processes governing the evolution and interaction between astrophysical plasma electromagnetic fields. Transitional systems that showed changes from rotation-powered to accretion-powered states vice versa bridged populations radio accreting millisecond pulsars, eventually demonstrating evolutionary link envisaged by recycling scenario. A decade discoveries theoretical efforts just grasped complex phenomenology transitional gamma-ray bands. This chapter summarizes main properties three discovered so far, as well candidates related systems, discussing various models proposed cope with their multifaceted behaviour.