This paper proposes a brief tutorial on the high angular resolution techniques and especially for the case of optical long baseline interferometry. Through a review of published results in the field of circumstellar environments, we will show the great potential of interferometry in this field. We will conclude this paper by a description of the ESO-VLTI interferometer and show the new capabilities of MIDI and AMBER focal instruments for the stellar physic and especially for the study of circumstellar environments.