The nebulous term phase‐change material (PCM) simply refers to any substance that has a large heat of fusion and a sharp melting point. PCMs have been used for many years in commercial applications, mainly for heat management purposes. However, these fascinating materials have recently been rediscovered and applied to a broad range of technologies, such as smart drug delivery, information storage, barcoding, and detection. With the hope of kindling interest in this incredibly versatile range of materials, this Review presents an array of aspects related to the compositions, preparations, and emerging applications of PCMs. PCMs on the rise: As a result of their sharp melting points and large heats of fusion during phase transition, phase‐change materials (PCMs) have already found commercial use in thermal management. The vast potential of this class of fascinating materials has recently been tapped in a diverse array of high‐tech applications such as controlled release, information storage, sensing/detection, and barcoding.