In the early 1900s, mirror neurons (MNs) were discovered accidentally while performing experiments in the F5 brain area of monkeys. The neuroscientist Giacomo Rizzolatti and his colleagues were first to define MNs, which were located in the ventral premotor area F5 of macaque monkeys(Kilner and Lemon 2013). Following MN discovery in monkeys, scientists proposed the existence of MNs in humans. Since then, numerous studies have been conducted to support their existence in humans. MNs are structurally similar to other neurons, however, their unique feature is the ability to fire action potentials, not only when a subject is performing an action, but also when the subject is observing the same action performed by an experimenter (Cook et al. 2014). Over the years, through different studies, scientists have proposed the origin and functions of MNs. In this review, I present the different methods used to study MNs and their hypothesized functions. Most studies done in humans are based on functional magnetic resonance imaging (fMRI) and positron emission tomography (PET). However, considering the nature of these methods, it is difficult to derive conclusive evidence on the functions of MNs.