The innate immune system detects conserved microbial and viral determinants through pattern recognition receptors (PRRs), which initiate signaling events leading to immune responses. Recent research highlights the importance of a complex cellular infrastructure in innate immune signaling, enabling spatial regulation of microbial detection and immune responses. Cell biological processes influence innate signaling, and innate signaling can drive cellular processes as defense or immunological memory. This review focuses on signals from the cell surface, endosomes, and cytosol. PRRs are classified into five families: TLRs, CLRs, NLRs, RLRs, and ALRs. TLRs, CLRs, and NLRs are membrane-bound or intracellular, detecting extracellular and intracellular pathogens. TLR4, a key TLR, signals via a multireceptor complex involving LBP, CD14, and MD-2. TLR4 signaling from the plasma membrane requires adaptor proteins like TIRAP and MyD88, which initiate NF-κB and IFN responses. TLR4 also undergoes endocytosis to engage TRAM/TRIF signaling from endosomes, regulating immune responses. Endosomal signaling by TLRs, such as TLR3 and TLR7/9, involves distinct pathways. TLR3 activates TRIF-dependent signaling, while TLR7/9 use MyD88-dependent pathways in plasmacytoid DCs. These pathways are spatially regulated, with TLR7/9 signaling occurring in distinct endosomal compartments. TLRs like TLR9 recognize unmethylated CpG DNA, while TLR7 and TLR3 detect RNA. These receptors are synthesized in an inactive state and require proteolytic cleavage to become active. NOD1 and NOD2, cytosolic NLRs, detect bacterial components and signal through RIPK2, activating NF-κB and MAPK. These receptors also regulate autophagy to eliminate intracellular pathogens. NOD1/2 are recruited to endosomal membranes, where they initiate signaling. RLRs, including RIG-I and MDA5, detect cytosolic RNA. RIG-I and MDA5 activate MAVS through CARD interactions, leading to IFN and proinflammatory cytokine production. MAVS signaling is regulated by membrane localization and receptor recruitment. RLR signaling occurs at mitochondria, peroxisomes, and MAMs, with distinct antiviral gene expression profiles. The biosynthetic pathway detects foreign nucleic acids, serving as markers of infection. PRRs like RLRs and NLRs survey this compartment, coordinating immune responses to intracellular pathogens. Cell biological features, such as receptor localization and adaptor interactions, regulate innate immune signaling, ensuring precise and effective immune responses.The innate immune system detects conserved microbial and viral determinants through pattern recognition receptors (PRRs), which initiate signaling events leading to immune responses. Recent research highlights the importance of a complex cellular infrastructure in innate immune signaling, enabling spatial regulation of microbial detection and immune responses. Cell biological processes influence innate signaling, and innate signaling can drive cellular processes as defense or immunological memory. This review focuses on signals from the cell surface, endosomes, and cytosol. PRRs are classified into five families: TLRs, CLRs, NLRs, RLRs, and ALRs. TLRs, CLRs, and NLRs are membrane-bound or intracellular, detecting extracellular and intracellular pathogens. TLR4, a key TLR, signals via a multireceptor complex involving LBP, CD14, and MD-2. TLR4 signaling from the plasma membrane requires adaptor proteins like TIRAP and MyD88, which initiate NF-κB and IFN responses. TLR4 also undergoes endocytosis to engage TRAM/TRIF signaling from endosomes, regulating immune responses. Endosomal signaling by TLRs, such as TLR3 and TLR7/9, involves distinct pathways. TLR3 activates TRIF-dependent signaling, while TLR7/9 use MyD88-dependent pathways in plasmacytoid DCs. These pathways are spatially regulated, with TLR7/9 signaling occurring in distinct endosomal compartments. TLRs like TLR9 recognize unmethylated CpG DNA, while TLR7 and TLR3 detect RNA. These receptors are synthesized in an inactive state and require proteolytic cleavage to become active. NOD1 and NOD2, cytosolic NLRs, detect bacterial components and signal through RIPK2, activating NF-κB and MAPK. These receptors also regulate autophagy to eliminate intracellular pathogens. NOD1/2 are recruited to endosomal membranes, where they initiate signaling. RLRs, including RIG-I and MDA5, detect cytosolic RNA. RIG-I and MDA5 activate MAVS through CARD interactions, leading to IFN and proinflammatory cytokine production. MAVS signaling is regulated by membrane localization and receptor recruitment. RLR signaling occurs at mitochondria, peroxisomes, and MAMs, with distinct antiviral gene expression profiles. The biosynthetic pathway detects foreign nucleic acids, serving as markers of infection. PRRs like RLRs and NLRs survey this compartment, coordinating immune responses to intracellular pathogens. Cell biological features, such as receptor localization and adaptor interactions, regulate innate immune signaling, ensuring precise and effective immune responses.