Lighting is no longer just a tool for visibility; it is a biological regulator that directly influences hormone production within the human body. In this context, the concept of Human-Centric Lighting (HCL) has emerged, aiming to replicate the natural cycle of sunlight within indoor environments. Research shows that exposure to strong blue light in the evening—emitted by modern lighting systems and digital screens—suppresses the production of melatonin, the hormone responsible for regulating sleep. This disruption can lead to sleep disorders and increase the risk of long-term health issues such as diabetes and depression. Conversely, smart lighting systems that adjust their color temperature throughout the day—from approximately 6500 Kelvin during daylight hours to 2700 Kelvin in the evening—help regulate the body’s internal clock. This promotes alertness during the day and supports deeper, more restful sleep at night. The article also highlights the importance of lighting distribution within spaces. Indirect lighting directed toward ceilings creates a sense of openness and psychological comfort, while task lighting enhances visibility and reduces eye strain during focused activities. Another key consideration is the management of glare, which can cause visual discomfort. This can be addressed through proper lighting angles and the use of matte finishes that minimize harsh reflections. Ultimately, well-designed lighting achieves a balance between energy efficiency and biological performance. In doing so, light becomes a form of “silent therapy”—enhancing mood, supporting well-being, and reinforcing its role as a fundamental element of modern interior design.