Over the last two decades, many efforts have been devoted to the search for brown dwarfs, and various ways of finding them have been developed. Deep photometric surveys in nearby open clusters is one approach that has provided a large amount of candidates. These clusters offer a number of advantages (a single known distance, metallicity and age) that make feasible the identification of such once elusive objects. Moreover, deep searches constitute one of the most direct means of measuring the mass function through the whole stellar and substellar mass range. In this paper the progress is presented of recent work on several young open clusters which leads to the finding of unambiguous brown dwarfs beyond the substellar mass limit. These discoveries, particularly in the Pleiades, imply a mass function in the substellar domain down to 0.05 Modot which can be fitted by a power law with α = -0.8 +/- 0.2 ({d}N / {d}M ~Mα). The detection of reliable candidate members with estimated masses of only 0.02-0.015 Modot in younger clusters, such as σ Orionis, provides substantial evidence for the initial mass function extending down to the deuterium-burning mass limit.