Abstract
Characterizing large samples of young stars and studying the dynamical evolution of stellar clusters are the main subjects of this paper. The review is based on multi-band observations of star-forming regions, as well as the clustering properties observed in the spatial distribution of stars in young clusters, compared with N-body simulations that reproduce their fractal sub-structures. These are recent observational and theoretical results related to the early phases of the clusters evolution, whose initial star-forming conditions could be under effect of ionizing sources.
