Circadian typology (CT) refers to individual differences in circadian rhythms, classified into three chronotypes: morning (MT), neither (NT), and evening (ET). CT is measured using self-report questionnaires and biological markers such as sleep-wake cycles, body temperature, cortisol, and melatonin. CT influences biological and psychological functioning, affecting health and disease. CT is influenced by individual factors (age, sex), environmental factors (photoperiod, light exposure), and genetic factors. CT is associated with cognitive performance, personality traits, and psychiatric disorders. CT also affects adjustment to shift work and jet-lag. The MEQ and rMEQ are widely used CT measures, with the rMEQ being a shorter, more reliable version. The CSM and MA scales are also used to assess CT. The PS, CTQ, and MCTQ are other CT measures. CT is influenced by age, sex, and environmental factors such as photoperiod and longitude. Genetic factors also play a role, with polymorphisms in clock genes like PER3 associated with CT. CT is linked to sleep-wake timing, body temperature, cortisol, and melatonin. CT is important for adjusting to shift work and jet-lag, with MT generally better adapted to morning work and ET to evening work. CT is also linked to cognitive performance, with MT showing better performance in the morning and ET in the evening. CT is a complex phenotype influenced by multiple genetic and environmental factors. CT is important for understanding human behavior and has implications for health, work, and clinical practice.Circadian typology (CT) refers to individual differences in circadian rhythms, classified into three chronotypes: morning (MT), neither (NT), and evening (ET). CT is measured using self-report questionnaires and biological markers such as sleep-wake cycles, body temperature, cortisol, and melatonin. CT influences biological and psychological functioning, affecting health and disease. CT is influenced by individual factors (age, sex), environmental factors (photoperiod, light exposure), and genetic factors. CT is associated with cognitive performance, personality traits, and psychiatric disorders. CT also affects adjustment to shift work and jet-lag. The MEQ and rMEQ are widely used CT measures, with the rMEQ being a shorter, more reliable version. The CSM and MA scales are also used to assess CT. The PS, CTQ, and MCTQ are other CT measures. CT is influenced by age, sex, and environmental factors such as photoperiod and longitude. Genetic factors also play a role, with polymorphisms in clock genes like PER3 associated with CT. CT is linked to sleep-wake timing, body temperature, cortisol, and melatonin. CT is important for adjusting to shift work and jet-lag, with MT generally better adapted to morning work and ET to evening work. CT is also linked to cognitive performance, with MT showing better performance in the morning and ET in the evening. CT is a complex phenotype influenced by multiple genetic and environmental factors. CT is important for understanding human behavior and has implications for health, work, and clinical practice.