The chapter discusses the interactions among microbes within the plant holobiont, emphasizing the complex relationships between plants and their associated microbial communities. It highlights how selective pressures have shaped these communities, leading to the evolution of host-adapted microorganisms that impact plant fitness. The text also explores the importance of microbe-microbe interactions in sculpting microbial assemblages in various plant compartments, such as the phyllosphere, rhizosphere, and endosphere. While reductionist approaches have been crucial in understanding specific microbial strategies, the chapter emphasizes the need for more comprehensive studies to understand the broader implications of these interactions on plant health in natural contexts. Key mechanisms discussed include nutritional interdependencies, biofilm formation, molecular communications, enhanced dispersal, bacterial endosymbiosis, and competitive interactions. The chapter also reviews the role of intermicrobial interactions in shaping plant-associated microbial communities, promoting plant growth, and suppressing diseases. Finally, it underscores the importance of microbial hubs and co-occurrence networks in modulating microbial community structure and plant health.The chapter discusses the interactions among microbes within the plant holobiont, emphasizing the complex relationships between plants and their associated microbial communities. It highlights how selective pressures have shaped these communities, leading to the evolution of host-adapted microorganisms that impact plant fitness. The text also explores the importance of microbe-microbe interactions in sculpting microbial assemblages in various plant compartments, such as the phyllosphere, rhizosphere, and endosphere. While reductionist approaches have been crucial in understanding specific microbial strategies, the chapter emphasizes the need for more comprehensive studies to understand the broader implications of these interactions on plant health in natural contexts. Key mechanisms discussed include nutritional interdependencies, biofilm formation, molecular communications, enhanced dispersal, bacterial endosymbiosis, and competitive interactions. The chapter also reviews the role of intermicrobial interactions in shaping plant-associated microbial communities, promoting plant growth, and suppressing diseases. Finally, it underscores the importance of microbial hubs and co-occurrence networks in modulating microbial community structure and plant health.