AbstractStar formation is inefficient. Recent advances in numerical simulations and theoretical models of molecular clouds show that the combined effects of interstellar turbulence, magnetic fields and stellar feedback can explain the low efficiency of star formation. The star formation rate is highly sensitive to the driving mode of the turbulence. Solenoidal driving may be more important in the Central Molecular Zone, compared to more compressive driving agents in spiral-am clouds. Both theoretical and observational efforts are underway to determine the dominant driving mode of turbulence in different Galactic environments. New observations with ALMA, combined with other instruments such as CARMA, JCMT and the SMA begin to reveal the magnetic field structure of dense cores and protostellar disks, showing highly complex field geometries with ordered and turbulent field components. Such complex magnetic fields can give rise to a range of stellar masses and jet/outflow efficiencies in dense cores and protostellar accretion disks.