Spots on the surface of HgMn stars: Clues to the origin of Hg and Mn peculiarities

The important result achieved in our recent study of a large sample of HgMn stars using UVES at the VLT and FEROS at the ESO 2.2m telescope is the finding that most HgMn stars exhibit spectral variability of various chemical elements, proving that the presence of an inhomogeneous distribution on the surface of these stars is a rather common characteristics and not a rare phenomenon.