 Exotons, quasi-particles of tightly bound electron-hole pairs, dominate the optical response of atomically thin transition metal decalcogenides. Here, the authors review strong light matter coupling in two-dimensional semiconductors, arising from confined exotons interacting with trapped photons, or localized plasmans. This article was authored by Christian Schneider, Mikhail M. Glasov, Tobias Korn, and others.