Tissue has characteristic properties when it comes to light absorption and scattering. For optical (OI) and optoacoustic imaging (OAI) these properties can be utilised to visualise endogenous chromophores, such as the oxygenation state of haemoglobin or melanin, as well as exogenously applied optical probes. Optical probes convert the energy of the light, typically laser, into either light of different wavelength, suited especially for fluorescent probes, or rather convert the energy into thermal expansion, favourable for optoacoustic imaging.