The amygdala, a brain region crucial for emotional processing, has long been associated with fear and reward. Recent technological advancements, particularly in rodents, have enabled causal investigations of specific neural circuits within the amygdala, revealing its complex anatomical connections and their impact on behavior. The amygdala is composed of multiple interconnected nuclei, including the basolateral complex (BLA) and the central nucleus of the amygdala (CeA). These circuits are involved in a wide range of behaviors, from fear conditioning to anxiety and reward processing. Lesion studies in non-human primates and rodents have shown that the amygdala is essential for emotional reactions to stimuli, such as fear and aggression. Fear conditioning, a simple associative learning process, has been extensively studied in rodents using Pavlovian conditioning, where a neutral stimulus is paired with an aversive event, leading to the acquisition of fear responses. Human studies using functional magnetic resonance imaging (fMRI) have confirmed the activation of the amygdala in response to fear-conditioned stimuli, with this activation waning during extinction. Recent studies have also explored the role of the amygdala in other behaviors, such as anxiety and feeding. For example, optogenetic manipulation of specific neuronal populations in the amygdala has revealed that the BLA–CeA circuit plays a role in anxiety-related behavior, with selective activation or inhibition of certain subpopulations of neurons affecting anxiety levels. Additionally, the BLA is involved in feeding suppression, with specific neuronal populations in the BLA being crucial for this process. The amygdala's role in reward processing is also well-documented. Lesions in the amygdala impair reward-based behaviors, such as place preference conditioning and conditioned orienting responses to reward-predictive cues. The BLA and CeA contribute differently to the representation of reward value, with the BLA representing outcome value along with specific sensory features, and the CeA maintaining a more general representation of motivational significance. Understanding the functional microcircuitry of the amygdala is crucial for advancing our knowledge of how neural signals affect behavior. Future research should focus on defining amygdala functional microcircuitry in preclinical models of human behavioral disorders, such as anxiety disorders, autism, and addiction. Additionally, there is a need to better understand how information from the amygdala affects downstream cortical circuits, which may play a role in decision-making and the integration of Pavlovian associations. Overall, the amygdala is a complex structure with multiple parallel circuits that contribute to a wide range of behaviors. Further research using advanced technologies and methods will continue to enhance our understanding of how neural signals in the amygdala influence behavior.The amygdala, a brain region crucial for emotional processing, has long been associated with fear and reward. Recent technological advancements, particularly in rodents, have enabled causal investigations of specific neural circuits within the amygdala, revealing its complex anatomical connections and their impact on behavior. The amygdala is composed of multiple interconnected nuclei, including the basolateral complex (BLA) and the central nucleus of the amygdala (CeA). These circuits are involved in a wide range of behaviors, from fear conditioning to anxiety and reward processing. Lesion studies in non-human primates and rodents have shown that the amygdala is essential for emotional reactions to stimuli, such as fear and aggression. Fear conditioning, a simple associative learning process, has been extensively studied in rodents using Pavlovian conditioning, where a neutral stimulus is paired with an aversive event, leading to the acquisition of fear responses. Human studies using functional magnetic resonance imaging (fMRI) have confirmed the activation of the amygdala in response to fear-conditioned stimuli, with this activation waning during extinction. Recent studies have also explored the role of the amygdala in other behaviors, such as anxiety and feeding. For example, optogenetic manipulation of specific neuronal populations in the amygdala has revealed that the BLA–CeA circuit plays a role in anxiety-related behavior, with selective activation or inhibition of certain subpopulations of neurons affecting anxiety levels. Additionally, the BLA is involved in feeding suppression, with specific neuronal populations in the BLA being crucial for this process. The amygdala's role in reward processing is also well-documented. Lesions in the amygdala impair reward-based behaviors, such as place preference conditioning and conditioned orienting responses to reward-predictive cues. The BLA and CeA contribute differently to the representation of reward value, with the BLA representing outcome value along with specific sensory features, and the CeA maintaining a more general representation of motivational significance. Understanding the functional microcircuitry of the amygdala is crucial for advancing our knowledge of how neural signals affect behavior. Future research should focus on defining amygdala functional microcircuitry in preclinical models of human behavioral disorders, such as anxiety disorders, autism, and addiction. Additionally, there is a need to better understand how information from the amygdala affects downstream cortical circuits, which may play a role in decision-making and the integration of Pavlovian associations. Overall, the amygdala is a complex structure with multiple parallel circuits that contribute to a wide range of behaviors. Further research using advanced technologies and methods will continue to enhance our understanding of how neural signals in the amygdala influence behavior.