Spintronics uses the electron spin, in addition to its charge, to store and process information. It underlies hard-disk read heads and magnetic memories (MRAM). In a direct-gap semiconductor such as GaAs, optical selection rules link the spin of the recombining carriers to the helicity, right or left circular, of the emitted photons. A light-emitting diode with a ferromagnetic contact, the spin-LED, therefore converts a magnetization into circularly polarized light. Since the first spin-LEDs in 1999 [1], perpendicularly magnetized injectors have been developed to emit along the surface normal without applied field. For two decades, however, the circular polarization remained below 10% at room temperature, and the helicity, set by the injector magnetization, could only be reversed by switching it with an external magnetic field. After an introduction to these concepts, I will show how a perpendicularly magnetized CoFeB/MgO injector reaches 36% circular polarization at room temperature without applied field, and allows the helicity to be reversed electrically through spin-orbit torque [2]. I will then present the next step: writing information while the LED is emitting. The helicity is reversed by 1.5 ns pulses while the LED remains continuously biased, which allows an image encoded in the photon helicity to be transmitted [3]. I will also show that this approach can be transferred to heterostructures grown by MOCVD, where interface preparation determines the polarization obtained at room temperature [4]. I will conclude with the transition to spin-lasers. In a laser, the nonlinear response near threshold can convert a small spin imbalance into almost fully polarized emission, and optically pumped spin-VCSELs show polarization oscillations above 200 GHz [5]. References [1] R. Fiederling et al., Nature 402, 787 (1999); Y. Ohno et al., Nature 402, 790 (1999). [2] P. A. Dainone et al., Nature 627, 783 (2024). [3] P. A. Dainone, R. Torrao-Victor et al., submitted (2026). [4] P. A. Dainone et al., manuscript in preparation. [5] M. Lindemann et al., Nature 568, 212 (2019).