The considerable attention paid to metal halide perovskites (MHP) and their low-dimensional (2D, 0D) nanostructures led in recent years to several scientific and technological advances, among which the creation of a new photovoltaic (PV) technology that competes with the most widespread ones [1]. With the ever-increasing diversity of applications explored, the need for fundamental understanding persists and may be gained either by smart and simple experimental protocols or models, or else via complex set-ups and computationally expensive ab-initio calculations. 2D MHPs combined with 3D MHP alloys help improving the stability of operating optoelectronic MHP devices [2]. The physics of these low-dimensional MHPs can be compared to conventional 2D materials [3], but the correct description of their properties still deserve further investigations [4-7]. MHPs colloidal nanocrystals [8] are a promising route to efficient light emitting devices, and more recently as potential single photon or correlated photon emitters [9]. The radiative recombinations in these 0D nanostructures are governed by excitons complexes [9]. The nature of the exciton ground state has been the topic of intense debate, especially after the Rashba effect was claimed to be responsible for an inverted bright/dark level ordering. The origin of the high brightness of these colloidal nanostructures is rather ascribed to an unusual coupling between the charge carriers and the ultrasoft MHP lattice [10-11]. [1] https://www.nrel.gov/pv/cell-efficiency.html [2] S. Sidhik et al, Deterministic fabrication of 3D/2D perovskite bilayer stacks for durable and efficient solar cells, Science 377, 1425(2022) [3] J.-C. Blancon et al, Semiconductor physics of organic-inorganic 2D halide perovskites, Nature Nano. 15, 969 (2020) [4] W. Li et al, Light-activated interlayer contraction in two-dimensional perovskites for high-efficiency solar cells, Nature Nano, 17, 45(2022) [5] Y. Qin, Dangling Octahedra Enable Edge States in 2D Lead Halide Perovskites, Adv. Mat. 34, 2201666 (2022) [6] H Zhang et al, Ultrafast relaxation of lattice distortion in two-dimensional perovskites, Nature Physics 19, 545 (2023) [7] C. Quarti et al, Exciton ground state fine structure and excited states landscape in layered halide perovskites from combined BSE simulations and symmetry analysis, Adv. Opt. Mat. 2202801(2023) [8] Q. Akkerman et al, Controlling the nucleation and growth kinetics of lead halide perovskite quantum dots, Science 377, 1406 (2022) [9] P. Tamarat et al, Universal scaling laws for charge-carrier interactions with quantum confinement in lead-halide perovskites, Nature Communications 14, 229 (2023) [10] P. Tamarat et al, The ground exciton state of formamidinium lead bromide perovskite nanocrystals is a singlet dark state. Nature Materials 18, 717 (2019). [11] B. Hehlen et al, Pseudospin-phonon pretransitional dynamics in lead halide hybrid perovskites Phys. Rev. B, 105, 024306 (2022)