This review presents a comprehensive overview about two-dimensional (2D) elemental materials termed Xenes. It highlights their fundamental properties, synthesis and encapsulation schemes, and the emergent Xene engineering trends, including reassembling three-dimensional materials made of the X element, derivatives materials which embed Xenes as building blocks, and Xenes hybrid obtained by combining different 2D materials. Finally, the fields where the Xenes are expected to provide innovative applications are discussed.