Histidine kinases (HKs) represent a core component of plant two-component signaling systems and serve as primary receptors for cytokinins, enabling plants to perceive developmental cues and respond to environmental stress. Recent studies have substantially expanded the understanding of HK diversification, receptor evolution, ligand-binding properties, and downstream signaling mechanisms, revealing their essential roles in regulating organogenesis, meristem activity, senescence, root–shoot communication, and responses to abiotic stresses. CHASE-domain-containing receptors have emerged as critical sensors with specialized cytokinin-binding capacities across species, while novel work has clarified the broad distribution and functional specificity of sensor HKs in eukaryotes. Additionally, receptor-like protein kinases (RLKs) have been implicated in complementary and overlapping functions during abiotic stress acclimation, further integrating hormonal, metabolic, and environmental signals. This review synthesizes current advances in HK biology, cytokinin receptor evolution, molecular structure, physiological functions, and their involvement in developmental processes such as shoot organogenesis, leaf aging, embryonic patterning, and environmental adaptation. By consolidating findings across Arabidopsis, maize, apple, and other model systems, this paper highlights new insights into the complexity of HK signaling pathways and proposes future research directions for developmental biology and stress physiology.