Over the past decade, there is a growing research activity on light-matter interactions in atomically thin materials, such as graphene, topological insulators, thin polar and semiconducting layers and other van der Waals materials, including their heterostructures. Here, we will consider 2D ("flatland") materials as a promising rich platform for manipulation of infrared (IR) and terahertz (THz) waves. We will show how to launch and focus polaritons in graphene sheets and nano-cavities [1,2] and thin van der Waals multilayers (BN and graphene-BN hybrids) [3]. We will discuss both theoretical and experimental studies on 2D optics (optics in atomically-thick layers) as well as the applications of 2D plasmonics to modern IR and THz sensing and photodetecting optoelectronic nanodevices (see Fig.). Artistic representation of the concept of on-chip merging graphene photonics and electronics [3].