Published online by Cambridge University Press: 03 August 2017
This review deals with properties of very young (≤ 10–20 Myr) stellar clusters which are in the nebular phase and are embedded in photoionized regions (classical extragalactic HII regions (RHIIs) or starburst galaxies). Based on the analysis of the integrated light of these clusters at the UV and optical wavelengths, different techniques are discussed that allow to estimate in consistent the stellar content and the evolutionary state of the ionizing clusters. Figures illustrating this contribution can be found in: http://www.iaa.csic.es/∼rosa/