University of California Santa Barbara (UCSB) in the USA has reported on the use of tunnel junctions (TJs) to stack green and blue micro-sized light-emitting diodes (μLEDs) grown by metal-organic chemical vapor deposition (MOCVD) [Panpan Li et al,  Optics Express, vol29, p22001, 2021; Panpan Li et al, Appl. Phys. Lett., vol118, p261104, 2021].   The researchers comment: “The design enables the realization of cascaded blue/green μLEDs in one device with independent junction control, that is, we can control the blue μLED...