Graphene, after its synthesis and characterization in 2004 has revolutionized material research at the nanoscale. Despite the unique properties, e.g. high electrical conductivity, carrier mobility, and flexibility that this material offers, it cannot be used in practical applications due to the absence of a bandgap. Hence, a quest for other 2D materials that could complement Graphene began leading to the experimental realization of phosphorene which is an atomic monolayer of phosphorus atoms. It is a direct bandgap semiconductor and offers high carrier mobility, and offers a variety of allotropes that are structurally different and exhibit distinct properties. In this talk, I will discuss the structural, electronic, and optical properties of phosphorene allotropes, their heterostructures with other 2D materials, and their applications for devices.