Title: The observed multiplicity of low-mass stars: from embedded protostars to open clusters Author: G. Duchene The multiplicity of stars is a direct tracer of the conditions under which they form and, in particular, it provides constraints on the modes of fragmentation for pre-stellar cores. For several years, we and other groups have conducted systematic surveys for the multiplicity of solar-like and lower-mass stars in nearby young (a few to a few hundred million years) open clusters to search for evidence of the influence of the environmental conditions during the star formation process and/or dynamical effects such as a general decrease or increase of the stellar multiplicity. While these surveys have led to the conclusion that the multiplicity of low mass stars is essentially established by the age of a few million years at most, they have left open the possibility that significant changes occur in the earlier, more embedded phases of stellar evolution. We have recently began a statistical survey for multiplicity among embedded protostars in order to probe such phenomena. In this talk, I will summarize both types of surveys, i.e., the multiplicity of low-mass stars in young open clusters and that of embedded protostars. Direct and high-angular resolution imaging has been used, leading to the discovery of tens of companions and providing statistically significant multiplicity rates that can be compared to model predictions.