My talk reviews recent developments of the research in spin electronics at Unité Mixte de Physique in Orsay. I will focus on the three following topics: 1)Magnetization reversal by injection of a spin-polarized current: After an introduction on the effect predicted by Slonczewski (and also Berger), I will present experimental results obtained on pillar-shaped trilayers (collaboration with LPN-CNRS and University of Brest) and I will describe the pending problems in the understanding of the spin transfer mechanisms generating the reversal. Current-induced reversal could lead to general applications for the switching of spin electronic devices and I will present the perspective in this direction. 2)Magnetic tunnel junction (MTJ): Although applications of the magnetoresistance (TMR) of MTJ are already around the corner, physics of spin-polarized tunneling is still far from being clearly understood. I will present experimental results on epitaxial (single crystal) MTJ which shed light on the physical mechanisms of TMR. 3)Spin injection into semiconductors: the development of devices combining ferromagnets and semiconductors is an important challenge in spin electronics. I will present a model clearing up the conditions for efficient spin injection from a ferromagnetic metal into a semiconductor.