3D halide perovskites with formula ABX3 have demonstrated exceptional photoelectric performance. In this structure, a divalent metal cation (B site; e.g., Sn 2+ and Pb 2+ ) coordinates to six halide anions (X site; e.g., I -, Br -, and Cl -) to form a BX6 octahedral framework. Furthermore, a monovalent cation (A site; e.g., MA + , FA + , and Cs + ) occupies the centers of four BX6 octahedra. Nonetheless, the lack of stability continues to hinder the commercialization of MHP film-based devices. Recent studies have shown that the inclusion of long-chain organic cation spacers in 3D perovskite can produce 2D perovskite, which enhances the film's stability against aging and decomposition caused by exposure to water and oxygen. Specifically, 2D perovskite is typically represented by the formula (A')m(A)n-1BnX3n+1. This formula includes divalent (Dion Jacobson m=1) or monovalent (Ruddlesden-Popper m=2) cations that connect the (A)n-1BnX3n+1 2D sheets, forming a monolayer or a bilayer, respectively. The thickness of the metal halide sheets can be adjusted by tuning the precursor composition, with n indicating the sheet number of perovskite layers. The benefits of the 2D perovskite structure have led to its widespread use as an absorber layer or capping layer to enhance the stability of MHP-based devices. Despite the progress made in fabricating various types of 2D MHP films, the crystallization process during thermal annealing remains challenging to comprehend. This is mainly due to the rapid, hardly controllable, and random formation of multiple 2D structures. Consequently, it becomes difficult for researchers to optimize the crystal quality and, subsequently, to improve the devices performances. Therefore, it is crucial to acquire a systemic comprehension of the crystallization growth mechanism during thermal annealing over the compositions ranging from 2D to 3D. Herein, we unveil the growth mechanism of complex m=2 Ruddlesden-Popper perovskite films with various dimensionalities. We cover the range from 2D (n = 1), Quasi-2D (2 ≤ n ≤ 5), to Quasi-3D (6 ≤ n) MHP films and compare them to the 3D (n = ) ones investigated in our previous work. For this purpose, we combine in situ grazing-incidence wide-angle X-ray scattering (GIWAXS), real-time glow-discharge optical emission spectrometry (GD-OES), time-of-flight secondary ion mass spectrometry (ToF-SIMs), scanning electron microscopy (SEM), and co-localized photoluminescence (PL) mapping measurements. These complementary techniques have enabled us to elucidate the intricated chronology and mechanism of phase formation, to observe shifts in their spatial distribution within the layer, to establish connections with solvent removal profiles and to understand the final products obtained.