Black phosphorus (BP) is a rapidly up and coming star in two-dimensional (2D) materials. The unique characteristic of BP is its in-plane anisotropy. This characteristic of BP ignites a new type of 2D materials that have low-symmetry structures and in-plane anisotropic properties. On this basis, they offer richer and more unique low-dimensional physics compared to isotropic 2D materials, thus providing a fertile ground for novel applications including electronics, optoelectronics, molecular detection, thermoelectric, piezoelectric, and ferroelectric with respect to in-plane anisotropy. This article reviews the recent advance in characterization and applications of in-plane anisotropic 2D materials.