4 planets have been detected so far with the microlensing technique. We will show that 
follow up observations by the second generation of VLTI instrumentation will allow us to 
directly detect the lens and greatly improve our knowledge of the systems : By detecting the 
lens star, we will obtain accurate determination of the mass of the planet, and its orbital 
separation.
We will use OGLE-2005-BLG-390Lb (~5.5 Earth mass orbiting a red dwarf at ~2.8 AU) as an illustration.