High intensity beams are difficult to be produced and controlled as collective effects, and impedances create fast emittance growth or beam deformations. In addition to fast coherent effects, space charge is also responsible of incoherent effects (complex nonlinear detuning) which couple with machine nonlinearities. For bunched beams the co-existence of machine nonlinearities and of space charge originates very complex nonlinear diffusional regimes, which becomes relevant for long term storage of bunches. In the decade 2000 - 2010 the numerical and experimental studies have concerned the interplay of space charge, and one dimensional resonances (3 Qx = N, and 4 Qx = N). In the years after 2012 the quest for unravelling the beam dynamics in presence of coupled resonances type Qx+2Qy=N and space charge has been pursued with experiments, simulations, and theory. In this talk an overview, and state of the art of this subject is presented.