The birth of stars at the low mass end of main sequence is investigated. Possible deuterium-burning shells slightly increase the critical mass for H burning which is about 0.08 solar masses for homogeneous stellar models with pop I composition, since the degree of central condensation is higher for inhomogeneous models than for those of homogeneous one. When hydrostatic protostellar core reaches the critical mass, H-flash takes place, provided that the accretion rate is so small that cores can radiate enough entropy for electron gas to become degenerate. H-flash develops vigorous convective motion of magnetized rotating medium, resulting in strong stellar wind phase, and stellar winds break surrounding molecular clouds mainly in the direction of the rotation axis. Stars flare up, settle on the Hayashi track and then descend as T-Tauri stars. Some of bipolar flows in star forming regions may be initiated at the onset of H-flash while progenitors(protostars or accreting brown-dwarf cores) are embedded within dense molecular clouds. Brown dwarfs form rarely and are not the main constituent of galactic dark matter, since protostars continues to receive surrounding matter. Low mass end of initial mass function depends critically on whether H-flash takes place frequently or not.