With the discovery of mechanically exfoliated graphene in 2004, two-dimensional (2D) nanomaterials have emerged as one of the most promising candidates in the fields of chemistry, material science, physics, and nanotechnology due to their unique physical, chemical, optical and electronic properties. In this Review, we briefly introduce the general synthetic strategies applied to 2D nanomaterials, followed by describing some important and newly developed members of the 2D family. Then, we discuss in detail the engineering strategies to enhance their intrinsic performance for extensive applications among the electrocatalysis, photocatalysis, energy storage, and bioimaging. Finally, the challenges and outlooks in these fields are also addressed.