Metal halide perovskites (MHPs) have emerged as promising materials for optoelectronics and photonics, mostly due to their large absorption coefficient and excellent photoluminescence quantum yield at room temperature, being a drawback their stability under ambient conditions. Particularly, MHPs in the form of nanocrystals are useful for the fabrication of optoelectronic and photonic devices by using inkjet printing and similar solution processing techniques. For these applications it is very important to know the limitations of nanocrystal MHPs for such applications that are imposed by the exciton recombination dynamics. In this way, our “delayed photoluminescence model” will be explained in this talk as the basis to understand the role of shallow non-quenching traps on the observed exciton recombination dynamics as a function of temperature [1,2]. Another key point for the development of active photonic devices (e.g., optical amplifiers and lasers) is the observation of stimulated emission at room temperature, which was possible at very low thresholds in MHP films integrated on polymer waveguides both on rigid and flexible substrates [3,4]. In the case of films prepared by CsPbX₃ (X₃ = Br₃, X₃ = Br_1.5I_1.5, X₃ = I₃) nanocrystals with different thicknesses we have demonstrated Amplified Spontaneous Emission (ASE) in backscattering geometry for a wide range of temperatures [5]. In these films we demonstrated ASE thresholds lower than 5 μJ/cm2 at cryogenic temperatures under nanosecond laser excitation and the physical origin of ASE was elucidated (single exciton origin in contrast to biexcitonic, as claimed in literature). At single nanocrystal level, the emission properties of nanocrystals can be also profited for other applications, as near-field imaging and single photon emitters. In the first case, the application related to single nanocrystals coupled to Mie resonators formed by TiO2 nanoparticles will be presented [6], whereas in the second case the coupling of perovskite nanocrystals to the optical modes of hyperbolic metal-dielectric metamaterials (HMMs) will be examined [7]. For TiO2-perovskite resonators a notable absorption enhancement is observed at the level of an optical probe whose extent is around 100 nm [6] and for the HMM-perovskite a Purcell enhancement of its radiative rate very close to a factor 4 was recently demonstrated (paper in press).