Chemical and physical processes in the earliest phases of star formation

The initial conditions in the process of star and planet formation are
to be found in pre-stellar cores, which are dense (n_H > 10^5 cm-3),
cold (T < 10 K), centrally concentrated and gravitationally
contracting regions embedded in molecular clouds. Knowledge of the
physical structure and kinematics of pre-stellar cores is needed to
put constraints on theories of star and planet formation. This
requires a good understanding of the pre-stellar core chemical
structure, as spectral line profiles of trace species provide the only
diagnostics of the dynamics leading to star and planet
formation. Because of their simple structure and quiescent nature,
pre-stellar cores are also ideal laboratories in which to measure key
astrophysical processes and parameters. I will review work on
pre-stellar cores in low-mass star-forming regions, showing Herschel
observations and how ALMA will unveil the still unexplored central few
hundreds AU of pre-stellar cores, the future stellar system cradles.
I'll then move to high-mass star-forming regions and show that our
work on nearby pre-stellar cores has provided a way to unveil massive
starless cores and test star formation theories. Cycle 0 ALMA and OT2
Herschel data will be presented.