Recent Developments In Heavy Quarkonium Physics

Recent developments in heavy quarknoium physics are reviewed in brief, including (i) nonrelativistic QCD(NRQCD), (ii) the importance of color-octet $(Q\bar{Q})$ components in the decay and the production of a physical heavy quarkonium state, (iii) limitation of the NRQCD factorization and (iv) the double humps in the $\pi\pi$ spectrum in the decay $\Upsilon(3S) \to \Upsilon (1S) \pi\pi$.