What can we Learn from the Fragmentation of Halo Nuclei?

A review of a series of experiments on the fragmentation of the Borromean nuclei ⁶He, ⁸He, ¹¹Li and ¹⁴Be is given. The aim of this review is to discuss the different kinematical observables which reflect in the most straightforward way either the reaction mechanism or the structure of the nucleus. The particle knock-out is found to play a significant role in all the cases under investigation. This channel is shown to be most informative with regard to the nuclear structure. Perspective experiments with a cluster knock-out are discussed.