The article reviews the two fundamental bacterial small-molecule signaling pathways: extracellular quorum-sensing signaling and intracellular cyclic dinucleotide (cdiGMP) signaling. Quorum sensing involves the production, release, and detection of autoinducers by bacteria to coordinate gene expression based on population density. Two main types of autoinducers are used: acyl homoserine lactones (AHLs) by Gram-negative bacteria and modified oligopeptides by Gram-positive bacteria. AHLs are synthesized by LuxI-type synthases and detected by LuxR-type proteins, while oligopeptide autoinducers are detected by membrane-bound two-component signaling proteins. The article highlights two notable autoinducers, PQS (Pseudomonas quinolone signal) and AI-2, which play crucial roles in virulence and interspecies communication, respectively. PQS, produced by *Pseudomonas aeruginosa*, is transported between cells via membrane vesicles, facilitating quorum sensing and biofilm formation. AI-2, produced by a wide variety of bacteria, enables interspecies communication and can be recognized by different bacterial species. Intracellular cdiGMP signaling involves the synthesis and breakdown of cdiGMP by diguanylate cyclases (DGCs) and phosphodiesterases (PDEAs), respectively. cdiGMP functions as a common second messenger, regulating gene expression and cellular processes such as biofilm formation and virulence. The article discusses the role of cdiGMP in controlling gene expression and the potential for spatial restriction of cdiGMP to microdomains near the cytoplasmic membrane. It also explores the possible interplay between quorum sensing and cdiGMP signaling, suggesting that these two pathways may converge to control complex processes like biofilm formation, multicellularity, and virulence. The article concludes by highlighting the importance of understanding the molecular mechanisms underlying these signaling pathways and their implications for bacterial behavior and disease.The article reviews the two fundamental bacterial small-molecule signaling pathways: extracellular quorum-sensing signaling and intracellular cyclic dinucleotide (cdiGMP) signaling. Quorum sensing involves the production, release, and detection of autoinducers by bacteria to coordinate gene expression based on population density. Two main types of autoinducers are used: acyl homoserine lactones (AHLs) by Gram-negative bacteria and modified oligopeptides by Gram-positive bacteria. AHLs are synthesized by LuxI-type synthases and detected by LuxR-type proteins, while oligopeptide autoinducers are detected by membrane-bound two-component signaling proteins. The article highlights two notable autoinducers, PQS (Pseudomonas quinolone signal) and AI-2, which play crucial roles in virulence and interspecies communication, respectively. PQS, produced by *Pseudomonas aeruginosa*, is transported between cells via membrane vesicles, facilitating quorum sensing and biofilm formation. AI-2, produced by a wide variety of bacteria, enables interspecies communication and can be recognized by different bacterial species. Intracellular cdiGMP signaling involves the synthesis and breakdown of cdiGMP by diguanylate cyclases (DGCs) and phosphodiesterases (PDEAs), respectively. cdiGMP functions as a common second messenger, regulating gene expression and cellular processes such as biofilm formation and virulence. The article discusses the role of cdiGMP in controlling gene expression and the potential for spatial restriction of cdiGMP to microdomains near the cytoplasmic membrane. It also explores the possible interplay between quorum sensing and cdiGMP signaling, suggesting that these two pathways may converge to control complex processes like biofilm formation, multicellularity, and virulence. The article concludes by highlighting the importance of understanding the molecular mechanisms underlying these signaling pathways and their implications for bacterial behavior and disease.