  Recent observations of microlensing events in the Large Magellanic Cloud
suggest that a sizable fraction of the galactic halo is in the form of Massive
Astrophysical Compact Halo Objects (MACHOs). Although the average MACHO mass is
presently poorly known, the value $\sim 0.1 M_{\odot}$ looks as a realistic
estimate, thereby implying that brown dwarfs are a viable and natural candidate
for MACHOs. We describe a scenario in which dark clusters of MACHOs and cold
molecular clouds (mainly of $H_2$) naturally form in the halo at galactocentric
distances larger than 10-20 kpc. Moreover, we discuss various experimental
tests of this picture.
