balance and, hence, climate. For example, biogenic aerosols in remote marine environments (for example, the Southern Ocean) can increase the number and size of cloud droplets, having similar effects on climate as aerosols in highly polluted regions. Specifically, phytoplankton emit dimethylsulfide, and its derivate sulfate promotes cloud condensation. Understanding the ways in which marine phytoplankton contribute to aerosols will allow better predictions of how changing ocean conditions will affect clouds and feed back on climate. In addition, the atmosphere itself contains about 1022 microbial cells, and determining the ability of atmospheric microorganisms to grow and form aggregates will be valuable for assessing their influence on climate. After the tantalizing detection of phosphine (PH3) in the atmosphere of the Venus planet, and in the absence of a known and plausible chemical mechanism to explain the formation of this molecule, Greaves et al. speculated in 2020 that microorganisms might be present in suspension in the Venus atmosphere. They have formulated the hypothesis of the microbial formation of phosphine, envisaging the possibility of a liveable window in the Venusian clouds at a certain altitude with an acceptable temperature range for microbial life. However, in 2021 Hallsworth et al. examined the conditions required to support the life of extremophile microorganisms in the clouds at high altitude in the Venus atmosphere where favorable temperature conditions might prevail. Beside the presence of sulfuric acid in the clouds which already represent a major challenge for the survival of most of microorganisms, they came to the conclusion that the Venus atmosphere is too dry to host microbial life. They determined a water activity ≤ 0.004, two orders of magnitude below the 0.585 limit for known extremophiles. Airborne microbiomes While the physical and chemical properties of airborne particulate matter have been extensively studied, their associated airborne microbiome remains largely unexplored. Microbiomes are defined as characteristic microbial communities, which include prokaryotes, fungi, protozoa, other micro-eukaryotes and viruses, that occupy well-defined habitats. The term microbiome is broader than other terms, for example, microbial communities, microbial population, microbiota or microbial flora, as microbiome refers to both its composition (the microorganisms involved) and its functions (their members' activities and interactions with the host/environment), which contribute to ecosystem functions. Throughout Earth's history, microbial communities have changed the climate, and climate has shaped microbial communities. Microorganisms can modify ecosystem processes or biogeochemistry on a global scale, and we start to uncover their role and potential