Brown dwarfs are the objects that bridge the realms of stars and planets, making them
important benchmarks for testing star and planet formation theories. In particular,
studies of brown dwarfs at young ages are crucial for understanding the mass dependence
in the formation and early evolution of stars. Star forming regions and young clusters
harbour large populations of these substellar objects, including some with masses comparable
to those of giant planets. Our deep survey SONYC (Substellar Objects in Nearby Young
Clusters) was designed to provide a census of the substellar population in nearby star
forming regions, and characterize their Initial Mass Functions down to unprecedented masses
below 10 MJup. In this talk I will present the current status of the studies of the
low-mass IMF, discuss the effects of environment, and outline the impact on our
understanding of star formation.