The formula of healthy light is the subject of more scientific research. We have developed our design scientifically to the best of our knowledge, also from practice by listening to people. The following aspects are important: - the amount of light (#lux on the eye), - the composition of light (a peak around 465Nm), - a full spectrum (colour rendering Ra >80), - the change of spectrum by day (from 4,800 to 1,800 kelvin), - the angle of incidence of light (oblique from the front and from above), - and the duration of exposure (4 hours per day, at least 30 minutes in the morning).