This Seminar is devoted to a series of papers written with T. Rivière. First, we have been interested in giving a unified proof of some “classical” quantization phenomena for problems such as harmonic maps, J-holomorphic curves or prescribed mean curvature. Then, since this proof relies only on the common dominator of theses problems, namely conformal invariance, we have been able to apply this theory to solve open questions in higher dimension, such as for bi-harmonic maps.