There is no doubt that optical coherence tomography has become an important biomedical imaging tool today especially due to recent improvements in detection as well as fight source technology. OCT achieves resolution in tissue of a few micrometers and can thus seen as the missing link between full body tomography methods such as CT and MRI on the one hand and microscopy on the other side. We give examples of tissue imaging as well as microscopy applications. Being based on interferometry OCT has the unique feature of providing also sample phase information. This information can be used to improve tissue contrast and even more to extract tissue perfusion parameters with high velocity sensitivity. It is well known that changes in blood flow and vascularization are early precursors of important diseases such as diabetes. Functional imaging extensions have therefore high clinical relevance. We show recent results obtained with Doppler OCT of micro-vascular retinal flow within full 3D volumes. An outlook of possible future directions in OCT research and development concludes the presentation.