Mitochondria are the powerhouses of all cells, producing energy needed to function in the form of adenosine triphosphate, ATP. However, energy production declines with age, leading to cell death, accelerated ageing and disease. Numerous studies in tissue culture and animal models have shown that exposure to long wavelength (red and near-infrared) light (photobiomodulation) improves mitochondrial function and energy (ATP) production, reducing cell death, improving health and extending lifespan. However, studies in humans have only shown indirect evidence of positive effects of long wavelength light, or have produced conflicting results. The current study will seek biological evidence of the effects of red light exposure in humans using magnetic resonance spectroscopy (MRS) to measure mitochondrial function (ATP levels) in the brain directly and noninvasively. Such evidence can inform the development of targeted therapies to combat neurodegenerative diseases and ageing.