Background: Educational research has been conducted mainly by using behavioural approaches. Whilst such methods provide invaluable insights into the field, several important questions such as 'how do we learn?' and 'what mechanisms cause individual differences?' cannot be answered thoroughly by using only behavioural approaches. In the last three decades, the advances of neuroimaging technologies and computational power have allowed researchers to investigate these questions beyond behavioural measures that provide complementary knowledge about human brain. Aim: One of the most recent neuroimaging techniques that holds much promise for use in educational settings is functional near-infrared spectroscopy (fNIRS). This article aims to introduce the fNIRS technique to educational researchers interested in neurocognitive mechanisms of academic learning and achievements to further promote the growing field of Educational Neuroscience. Method: We present the properties of the fNIRS device, its basic principles and important considerations when planning an fNIRS study. Results: Functional near-infrared spectroscopy is a portable, cost-effective and easy-to-handle neuroimaging device that allows experimentation in naturalistic settings such as in the school. Conclusion: Even though several articles describe different applications and technical features of the fNIRS technique, there is still a need for materials with a more accessible language for those unfamiliar with neuroscientific and technical terms.