A detailed control of light–matter interaction can be achieved by placing an optically active medium into a resonator. Here we want to demonstrate some aspects of such a control in semiconductors: In the first part of the article we will discuss the optical modes in microresonators with a three dimensional confinement of light (photonic dots) due to which the density of modes is dominated by sharp, discrete resonances. From optical spectroscopy insight into energies and field distributions of the modes is taken. More complicated confined photon geometries (photonic molecules) are obtained by connecting several photonic dots through narrow channels. The electromagnetic field distributions in these structures bear strong resemblences to bonding and anti-bonding orbitals in molecules. Also a model system of a photonic band gap structure can be created in this way: By increasing the number of coupled resonators in a linear chain the transition from an atomic- to a crystal-like system is obtained. The dependence of the band stucture on the geometry parameters as well as its modification by implementing defects have been studied in detail. In the second part we will then turn to the modification of light–matter interaction in photonic dots. Whereas for studying them, the optical modes were separated far from the electronic excitations, now the two excitations are brought in resonance. Both the regimes of weak and strong coupling are considered: In the strong coupling regime we observe the normal mode splitting of polaritons formed by a quantum well exciton and the several confined modes of photonic dots. The dependence of the Rabi splitting on the involved mode and on the resonator size is discussed. In the weak coupling regime we address the spontaneous emission of quantum dots that are embedded in photonic dots. Both an inhibition and a suppression of the emission could be demonstrated in resonators with a lateral metal coating.