It is well known that the nuclear shell structure changes for the most exotic nuclei, see [1] for example. One of the consequences of this phenomenon is the modification of the "classical" magic numbers, as experimentally observed at N=20 and N=28. Nevertheless, the mechanisms responsible for such changes are still under discussion and different experimental information is needed to better understand the change of the shell structure in these two regions and to better constrain the theoretical models. In this seminar, we are going to report on the experimental program we have carried out at GANIL and ISOLDE using different experimental probes: beta decay, isomeric decay, transfer reactions, in beam gamma spectroscopy, mass measurements. We will show how the intruder configurations progressively dominate the ground state structure of the most exotic nuclei at both N=20 and N=28.

[1] O. Sorlin and M. G. Porquet, Progress in Particle and Nuclear Physics, Volume 61, Issue 2, Pages 602