The coronal line region in AGN is an intermediate zone between the broad- and the narrow-line regions where lines with ionization potentials, IP >50 eV, are produced. Because these IP are not easily reachable in stars, coronal lines become unique tracers of the AGN activity. The coronal line region has so far remained unresolved as its typical size is of a few tens of pc. However, these sizes are now accessible to the diffraction limit of an 8 m telescope.