  Astrophysical masers are one of the most readily detected signposts of
high-mass star formation. Their presence indicates special conditions, probably
indicative of a specific evolutionary phase. Masers also represent the ultimate
high-resolution probe of star formation with the potential to reveal
information on the kinematics and physical conditions within the region at
milli-arcsecond resolution. To date this potential has largely remained
unfulfilled, however, recent advances suggest that this will soon change. The
key to unlocking the potential of masers lies in identifying where they fit
within the star formation jigsaw puzzle. I will review recent high resolution
observations of OH, water and methanol maser transitions and what they reveal.
I also briefly discuss how multi-transition observations of OH and methanol
masers are being used to constrain maser pumping models and through this
estimate the physical conditions in the masing region.
