This chapter begins with a general discussion on various techniques used to produce quantum-dot structures. It discusses literature on excitonic and plasma effects on GaN quantum dots and related structures, GaAs-based dots, In1-yGayAs-based dots and quantum dots containing P or Sb. Excitonic and biexcitonic effects and interlevel transitions are first presented. Topics discussed include work on linear optical spectra, Raman scattering in quantum dots, nonlinear optics, biexcitons and dynamical processes. The work on the influence of external fields on optical properties proceeding from stress via magnetic to electric fields is then reviewed. Finally, literature investigating plasma effects and lasing is presented.