Abstract The current generation of B-factories have given a major contributions in completing the spectrum of heavy quarkonia. New questions are raised above the thresholds, where many new states, the so called XYZʼs were found. Insight into their nature can come from the investigation of EM and hadronic transitions between them. This review will cover Belleʼs recent progress in this sector, which exploits the record samples of data taken on the peaks of the ϒ(2, 4, 5 S ) resonances: the discovery of two multiplets of charged bottomonia ( Z b ʼs) and of four S=1 states (parabottomonia), the studies on η transitions and on D-wave resonances in both charmonium and bottomonium. Prospects for future studies are given