This review summarizes the current understanding of primary biological aerosol particles (PBAP), which are biological materials and structures in the atmosphere, including microorganisms, spores, pollen, viruses, algae, and other biological particles. PBAP have significant impacts on atmospheric processes, such as cloud formation and climate, due to their ability to act as cloud condensation nuclei (CCN) and ice nuclei (IN). The review outlines the major categories of PBAP, including bacteria, archaea, fungal spores, pollen, viruses, algae, and lichens, and discusses their sources, characteristics, and concentrations. It also covers sampling methods and analytical techniques for PBAP, such as cultivation, microscopy, DNA/RNA analysis, and mass spectrometry. The review addresses the atmospheric relevance of PBAP, including their optical properties and their role in cloud and precipitation formation. It highlights the need for further research to better understand the impact of PBAP on the atmosphere and climate, including the development of efficient analytical techniques, the determination of PBAP abundance and diversity, and the study of their emission rates and atmospheric behavior. The review also discusses the importance of PBAP in various environments, such as urban, rural, marine, and high-altitude areas, and their potential influence on human health and ecosystems. Overall, the review emphasizes the need for continued research to improve our understanding of PBAP and their role in atmospheric processes.This review summarizes the current understanding of primary biological aerosol particles (PBAP), which are biological materials and structures in the atmosphere, including microorganisms, spores, pollen, viruses, algae, and other biological particles. PBAP have significant impacts on atmospheric processes, such as cloud formation and climate, due to their ability to act as cloud condensation nuclei (CCN) and ice nuclei (IN). The review outlines the major categories of PBAP, including bacteria, archaea, fungal spores, pollen, viruses, algae, and lichens, and discusses their sources, characteristics, and concentrations. It also covers sampling methods and analytical techniques for PBAP, such as cultivation, microscopy, DNA/RNA analysis, and mass spectrometry. The review addresses the atmospheric relevance of PBAP, including their optical properties and their role in cloud and precipitation formation. It highlights the need for further research to better understand the impact of PBAP on the atmosphere and climate, including the development of efficient analytical techniques, the determination of PBAP abundance and diversity, and the study of their emission rates and atmospheric behavior. The review also discusses the importance of PBAP in various environments, such as urban, rural, marine, and high-altitude areas, and their potential influence on human health and ecosystems. Overall, the review emphasizes the need for continued research to improve our understanding of PBAP and their role in atmospheric processes.