Sleep plays a critical role in learning and cognitive function, fundamentally shaping how the brain processes, stores and retains information. Different sleep stages support memory formation and consolidation, with distinct neural mechanisms aiding the transfer and strengthening of learned material. Sleep deprivation impacts cognitive performance well beyond memory, affecting abilities ranging from basic attention to complex decision-making. Neuroimaging and cognitive testing reveal how sleep loss impairs brain function, leading to measurable deficits that manifest in real-world consequences across various professional contexts, from medical errors to workplace accidents. Adolescents face particular vulnerability to sleep disruption due to their developing brains and shifting circadian rhythms. The relationship between sleep and cognition is bidirectional: mental strain can impair sleep quality, while inadequate sleep undermines cognitive performance. These findings carry significant implications for public health and workplace policies, highlighting the necessity of adequate sleep for optimal cognitive function and safety.