Abstract
What is long-baseline optical/IR stellar interferometry? A few years ago, many astronomers might not have been able to answer that question properly. This is today hopefully not the case anymore, because mainstream facilities, such as the VLTI, the Keck-I or the CHARA array, offer now this delicate technique to an astronomer who wants to observe his favourite object at the highest angular resolution available. The large teaching effort on what is interferometry and for what purpose it can be used, together with weak, but already convincing imaging capabilities, make the technique reaching a ``mature'' state. I will not discuss here the details of the technique, as already many booklets are now published on the subject, but rather describe what makes long-baseline stellar interferometry attractive for the field of hot star astrophysics.
