I present recent radiation hydrodynamical simulations that demonstrate
that X-rays from young stars may play an important but previously unsuspected
role - i.e that of evaporating gas from their circumstellar  discs.
Since these discs provide the birthplace of planets, a process that erodes
these discs has important implications for planet formation.
We demonstrate that this scenario is compatible with a range of diagnostics
such as the distribution of infrared colours of T Tauri stars as revealed
by Spitzer, together with blue-shifted emission lines in NeII and OI
in these systems. We show that the model provides a natural explanation
for the observed anti-correlation between X-ray luminosity and the possession
of a disc in young stars. Finally we highlight how disc studies at low 
metallicity may be used to determine whether photoevaporation or planet 
formation is the major mechanism for disc dispersal.