Published online by Cambridge University Press: 25 September 2002
We review the properties of stellar populations and the interstellarmedium (ISM) of various kinds of massive star forming regions(ranging from stellar clusters, Hii regions, super star clusters,etc. to distant starburst galaxies). The nature of their multi-wavelength spectra as well as the techniques used for their interpretation is are discussed.These objects play an important role in our understandingof star formation, interactions between stars and the ISM, and galaxyevolution among others.