Forward rapidity di-hadron azimuthal angular correlations in high energy proton-nucleus and proton-proton collisions are sensitive to quadrupoles; traceless correlator of 4 Wilson lines whereas single inclusive particle production iNVOLVES only dipoles, traceless correlator of 2 Wilson lines. We discuss the progress made in understanding the energy (rapidity) evolution of the quadrupole as well as its various limits.