Optical coherence tomography (OCT) originally started as an interferometric tool to investigate technical samples such as thin films with high precision. With the shift to biomedical applications OCT experienced a boost in detection performance. Novel methods such as Frequency domain OCT allow nowadays depth profile rates of more than 200 kHz. This trend is supported by new light source and detector technology. Fast 3D imaging in-vivo with resolution of a few micrometers is readily available as commercial instruments. Extensions of OCT such as polarization contrast, spectroscopic contrast, or Doppler measurements enrich the portfolio of applications in biology, medicine, and last but not least again in imaging and quality inspection of technical samples.