Mitochondria, traditionally viewed as energy producers, are now recognized as signaling organelles that interact with other cellular components. This review explores how mitochondria communicate with the nucleus under stress, highlighting mitonuclear signaling pathways that restore cellular homeostasis and promote longevity. Mitochondria, like midichlorians in Star Wars, are dynamic organelles that respond to stress by generating signals that modulate cellular defenses. Understanding mitochondrial signaling provides insights into disease susceptibility and lifespan extension. Mitochondria evolved from endosymbiotic bacteria, with two main theories: mitochondria-early and mitochondria-late. Both models involve gene transfer from the α-proteobacterium to the host. Mitochondria contain their own genome but most proteins are encoded by the nucleus. This gene transfer allows mitochondria to sense and respond to stress, producing signals that regulate nuclear gene expression. During stress, mitochondria release signals such as acetyl-CoA, reactive oxygen species (ROS), and calcium ions, which influence nuclear gene expression. Acetyl-CoA levels affect histone acetylation, regulating gene expression. ROS can act as stress signals, activating transcription factors and enhancing stress resistance. Calcium ions, released from mitochondria, trigger signaling pathways that regulate gene transcription and maintain calcium homeostasis. The mitochondrial unfolded protein response (UPRmt) is a protective pathway that enhances mitochondrial protein quality control and stress defense. The integrated stress response (ISR) integrates various stress signals, including mitochondrial and intercellular perturbations, to regulate translation and promote stress adaptation. Mitochondrial-derived peptides (MDPs), such as humanin and MOTS-c, are small peptides encoded in mitochondrial rRNA regions. These peptides play roles in energy homeostasis, cell survival, and apoptosis. MOTS-c, for example, can translocate to the nucleus under stress, activating genes involved in stress response and metabolic homeostasis. Mitochondrial stress signaling influences organism health and disease. ROS signaling can have both beneficial and detrimental effects on longevity. The UPRmt and ISR are involved in regulating mitochondrial function and disease susceptibility. MDPs, such as humanin and MOTS-c, are potential therapeutic targets for age-related diseases. In conclusion, mitochondrial signaling is crucial for cellular homeostasis and disease resistance. Understanding these pathways may lead to new therapeutic strategies for mitochondrial diseases and aging. The complex interplay between mitochondria and the nucleus highlights the importance of mitonuclear communication in maintaining cellular and organismal health.Mitochondria, traditionally viewed as energy producers, are now recognized as signaling organelles that interact with other cellular components. This review explores how mitochondria communicate with the nucleus under stress, highlighting mitonuclear signaling pathways that restore cellular homeostasis and promote longevity. Mitochondria, like midichlorians in Star Wars, are dynamic organelles that respond to stress by generating signals that modulate cellular defenses. Understanding mitochondrial signaling provides insights into disease susceptibility and lifespan extension. Mitochondria evolved from endosymbiotic bacteria, with two main theories: mitochondria-early and mitochondria-late. Both models involve gene transfer from the α-proteobacterium to the host. Mitochondria contain their own genome but most proteins are encoded by the nucleus. This gene transfer allows mitochondria to sense and respond to stress, producing signals that regulate nuclear gene expression. During stress, mitochondria release signals such as acetyl-CoA, reactive oxygen species (ROS), and calcium ions, which influence nuclear gene expression. Acetyl-CoA levels affect histone acetylation, regulating gene expression. ROS can act as stress signals, activating transcription factors and enhancing stress resistance. Calcium ions, released from mitochondria, trigger signaling pathways that regulate gene transcription and maintain calcium homeostasis. The mitochondrial unfolded protein response (UPRmt) is a protective pathway that enhances mitochondrial protein quality control and stress defense. The integrated stress response (ISR) integrates various stress signals, including mitochondrial and intercellular perturbations, to regulate translation and promote stress adaptation. Mitochondrial-derived peptides (MDPs), such as humanin and MOTS-c, are small peptides encoded in mitochondrial rRNA regions. These peptides play roles in energy homeostasis, cell survival, and apoptosis. MOTS-c, for example, can translocate to the nucleus under stress, activating genes involved in stress response and metabolic homeostasis. Mitochondrial stress signaling influences organism health and disease. ROS signaling can have both beneficial and detrimental effects on longevity. The UPRmt and ISR are involved in regulating mitochondrial function and disease susceptibility. MDPs, such as humanin and MOTS-c, are potential therapeutic targets for age-related diseases. In conclusion, mitochondrial signaling is crucial for cellular homeostasis and disease resistance. Understanding these pathways may lead to new therapeutic strategies for mitochondrial diseases and aging. The complex interplay between mitochondria and the nucleus highlights the importance of mitonuclear communication in maintaining cellular and organismal health.