Boron-based materials are subject of growing research interests and considered as potential future protective coating materials for diverse industrial sectors. Especially the class of transition metal diborides exhibits interesting properties not only for thermo-mechanical purposes (ultra-high temperature environments [1]) but also for electrochemical needs (HER and OER catalysts [2]). The exploration of boride films already started in the mid-1990s [3]. Still, it has been accelerated in the last decade due to new advances in PVD-based growth techniques and atomistic modeling, but also with the need for new alternatives in terms of future sustainability criteria. In addition, hexagonal diborides constitute the basis for developments of atomically layered MAB phases – obtaining at least 2-dimensional boron hexagon sheets in the simplest form. Exploring transition metal diborides poses specific challenges: (i) susceptible compositional and structural variety during plasma-assisted crystallization processes, (ii) anisotropy in their mechanical properties as well as brittle nature, and (iii) formation of non-adherent and volatile oxide scales. Within this talk, we want to address these specific challenges on various binary, ternary, and quaternary systems within group IV to VI transition metal diborides. Based on the limited kinetics during PVD-based growth, the phase formation has been investigated for diverse non-reactive deposition techniques (varied ionization degree by dcMS or HiPIMS) for WB2±z as a model system – also considering the influence of structural imperfections [4]. The anisotropic nature and the impact of B-rich tissue phases are thoroughly described for the super-hard TiB2±z system [5]. Furthermore, the tissue phase also governs the intrinsic fracture toughness (KIC) of these nano-crystalline TiB2±z films – obtaining a maximum of 3.55 ± 0.16 MPa√m for TiB2.22 [6]. In addition, step-wise alloying concepts from binary to quaternary diborides for enhancing the ductile character and oxidation resistance will be discussed in detail. Here, Si and disilicide alloying routes have been proven highly effective in providing long-term oxidation resistance up to 1200 °C [7-9]. To describe all these relations comprehensively, we correlated the synthesis parameters with structural and morphological evolution using XRD, HR-TEM, APT, ERDA, and micro-mechanical testing methods. Furthermore, atomistic modeling (DFT) has been used to describe specific aspects in exploring these diborides.