...a concept goes beyond that of a function for light stimulating specialized retinal ganglion cells to entrain circadian rhythms but extends this to include light having a direct influence on all neurons to potentially influence a range of core higher-order brain activities. ...the chlorophyll ingested by animals can be converted into metabolites that become incorporated within mitochondria across a number of body tissues. ...other wavelengths across the light spectrum have been reported to be absorbed by yet other chromophores. From a transcranial approach, light can penetrate down to the level of the cerebral cortex (Hamblin, 2016; Mitrofanis, 2019). ...light, being an electromagnetic wave, can potentially influence the activity and frequency of neurons in the large-scale neural networks, for example to influence the functional connectivity within the default mode network, as well as within and with the other networks, such as the central executive and salience ones Figure 1B. The significance of why light would have such an effect on these networks perhaps subserves a key survival strategy for the organism.