ABSTRACT
The introductory chapter introduces aeromicrobiology as a part of aerobiology essentially concerned with aerosolization, transmission, and deposition of microorganisms. Differential characteristics of the various strata of the atmosphere are described. The various groups of microorganisms, namely bacteria, archaea, fungi, protozoans, algae, and viruses, are examined, with particular attention to the forms and functions and propensity to become airborne. The indoor and outdoor sources of microorganisms as well as the natural and anthropogenic factors that modulate their aerosolization and survival in the air are elucidated. Molecular approach to sampling and analysis of bioaerosols samples is highlighted as a game changer in our understanding of airborne microbes. While emphasizing the long history of control of microorganism in the air dating back to the infancy of knowledge of germs, human-made biological agents and biocontrol agents are identified as a major threat to human existence, deserving attention, even as various conspiracy theories as in the case of SARS-CoV-2 remain unverified. © 2023 Elsevier Inc. All rights reserved.