Molecular clusters, formed through the aggregation of various atmospheric species, play a central role in aerosol particle formation, cloud nucleation, and chemical reactions, thus influencing climate, air quality, and environmental chemistry. The key species in cluster formation are believed to be inorganic molecules such as sulfuric acid, ammonia, and amines, enhanced by other species such as water, methanesulfonic acid, nitric acid, formic acid, and highly oxygenated organic molecules. Theoretical studies typically aim to elucidate the thermodynamics, kinetics, and molecular interactions governing cluster formation and its evolution. The main challenge for studying atmospheric molecular clusters is their complex configurational spaces, which require advanced configurational sampling techniques and computationally demanding quantum chemistry methods to evaluate the cluster properties accurately. Furthermore, atmospheric clustering is believed to be a multi-species process, adding another dimension of chemical complexity.