Plants exist as complex holobionts, whose health and productivity depend on dynamic interactions with diverse microbial partners. This chapter explores the ecological, molecular, and biotechnological dimensions of plant-microbe relationships, tracing the continuum from natural symbioses to their translation into microbe-based agricultural applications. It examines how plants actively structure their microbial communities across distinct yet interconnected compartments, such as the rhizosphere, phyllosphere, and endosphere, and how these microorganisms in turn modulate plant physiology, nutrient acquisition, and defense. Moving beyond the study of individual strains, we discuss the growing relevance of community-level approaches and synthetic microbial consortia as frameworks to decipher and replicate the ecological principles that sustain beneficial interactions. Finally, this chapter reflects on how the integration of ecological knowledge with emerging technologies such as synthetic biology, systems modeling, and artificial intelligence offers new opportunities to design resilient, predictable, and sustainable microbe-based solutions. By learning from these naturally optimized alliances, we can guide the transition to more adaptive and sustainable agricultural systems while sustaining plant health and productivity.