We show the integration of a home-made interference optical microscope (IOM) with an Atomic force microscope, as well as the combination of IOM with a nanoindentor. Such combined instruments have many applications in the characterisation of MEMS/NEMS. As an illustrative example, we have used a MEMS accelerometer with capacitive read-out. Surface topography and defects have been measured with an IOM/AFM setup, as well as the bending and the torsion of the inertial mass while a calibrated force is applied with the nanoindentor probe on an off-axis location of the inertial mass.