The purpose of this work is to construct a continuous map from the homogeneous Besov space B^02,4(R^2) in the set G of initial data in B^02,4(R^2) which gives birth to global solution of the mass critical non linear Schrödinger equation in the space L^4(R^1+2). We use the fact that solutions of scale which are different enough almost do not interact; the main point is that we determine a condition about the size of the scale which depends continuously on the data.