Abstract. The structure of heavy mesons located above the thresholds for the open flavor production has been largely discussed in the recent years. Their conventional description as pure BB bound state has been called into question by the study of the hadronic transitions to the lower states, and the observation of charged exotic states has highlighted the importance of the light quark degrees of freedom in the description of both charmonia and bottomonia. We will report the most recent experimental measurements performed by the Belle collaboration in the Y(4S), Y(5S) and Y(6S) regions, including the measurement of the ratio, the search for neutral states near the B 0B0 threshold, the first observation of the transition Υ(4S ) → ηh b (1P) and the study of the η transitions at the Υ(5S ) energy. The contribution to the study of the structure of these states coming from the measurement of hadronic transitions will be discussed.