Hyperons are believed to appear in the interior of neutron stars at around 2-3 times nuclear saturation density. Quantitative information on YN, YNN and YY interactions is indispensable to understand the high-density phases of neutron star matter, the occurrence of which may dramatically affect both the equilibrium and non-equilibrium properties of the star. Most theoretical models predict that the appearance of hyperons brings the maximum mass of a stable neutron star down to values incompatible with the recent observation of a star of about two solar masses. While there are indications that this problem may be overcome including the effect of YNN interactions, it may also signal the presence of a non-hadronic phase, i.e. of deconfined quark matter, in the inner core of the star. A large body of data came from two types of highly complementary hypernuclear spectroscopy techniques: reaction based spectroscopy (with hadron probes) and gamma spectroscopy. Both these powerful techniques have limitations, first limited energy resolution and small spin-flip amplitudes, and second the access only to hypernuclear states below nucleon emission threshold. The advantage of being able to simultaneously observe, by (e, e'K+) spectroscopy, more complete structures, as well as to provide precise absolute binding energy is obvious.