Phosphorene is a two-dimensional material consisting of phosphorus. It consists of a single layer of black phosphorus, the most stable allotrope of phosphorus. Phosphorene is analogous to graphene (single layer graphite). Among two-dimensional materials, phosphorene is a competitor to graphene because it has a nonzero fundamental band gap that can be modulated by strain and the number of layers in a stack. Phosphorene was first isolated in 2014 by mechanical exfoliation. Liquid exfoliation is a promising method for scalable phosphorene production.