Fiat lux (let there be light) – Genesis 1:3 These few words that, in the early 1990s, took on new meaning for neuroscience when researchers demonstrated that near-infrared light could be used to probe human brain function. That insight sparked what is now known as functional near-infrared spectroscopy (fNIRS): a non-invasive, portable neuroimaging technique that has exploded in popularity and grown from a handful of proof-of-concept experiments into a globally used research t