  We generalize the conventional Energy-Energy Correlator (EEC) to include the
azimuthal angle dependence, so to define azimuthal angle dependent EEC
observables. We study this new EEC observable in $e^+e^-$ and semi-inclusive
deep inelastic scattering (SIDIS). In the back-to-back region, we find that the
azimuthal angle dependent EEC is sensitive to both the unpolarized EEC jet
function and a Collins-type EEC jet function. While the unpolarized EEC jet
function is related to the unpolarized transverse momentum dependent (TMD)
fragmentation function, the Collins-type EEC jet function is connected with the
Collins fragmentation function. We further demonstrate how the new observables
allow us to access to the 3D structure of nucleons, especially the
spin-dependent ones.
