This paper proposes a brief tutorial on the high angularresolution techniques and especially for the case of optical longbaseline interferometry. Through a review of published results inthe field of circumstellar environments, we will show the greatpotential of interferometry in this field. We will conclude thispaper by a description of the ESO-VLTI interferometer and show thenew capabilities of MIDI and AMBER focal instruments for thestellar physic and especially for the study of circumstellarenvironments.