The original idea of OCT was to enable noninvasive optical biopsy, i.e., the in situ imaging of tissue microstructure with a resolution approaching that of histology without the need for tissue excision and processing.9 Thus, we have the following prerequisites: (1) visualization of subcellular morphology (i.e., ultrahigh isotropic resolution), (2) three-dimensional imaging (resulting in the need for ultrahigh imaging speed), (3) sufficient (tissue) contrast, (4) molecular, biochemical sensitivity (i.e., sensitive to absorption of diagnostically relevant endogenous or exogenous chromophores), (5) localized (quantitative) functional tissue information, and (6) sufficient (diagnostically relevant) tissue penetration. Axial resolution improvement (prerequisite 1) has been the key technological milestone in the history of OCT in its first decade,10–14 which has been achieved by using ultra-broadband sources. OCT imaging speed improvements (prerequisite 2) evolved in its second decade, which were accomplished by Fourier domain (FD)/spectral domain (SD)15–18 and swept source (SS) OCT.19–23 While in FD/SD OCT speed is mainly determined by the readout time of the camera in a spectrometer, the wavelength-tuning speed of swept sources is the decisive factor in SS OCT. In the past 5 to 10 years, different swept source technologies have emerged to significantly improve imaging speed in (commercial) OCT systems—especially the ones using wavelengths . In the present paper, the state-of-the-art (ultra)high-speed SS technologies are reviewed and compared (cf. Sec. 2.) and an outlook of even further improving OCT imaging speed via parallelization (line- and full-field OCT) of OCT detection is presented (cf. Sec. 3). OCT contrast enhancement (prerequisite 3) has been accomplished by introducing polarization-sensitive OCT,24–28 phase-sensitive OCT,29–33 optical coherence elastography,34–39 spectroscopic low coherence interferometry,40–43 elastic scattering spectroscopy,31,44–46 and nonlinear interferometric vibrational imaging (NIVI), as well as employing endogenous or exogenous contrast.47–52 In this paper, a recently developed contrast improvement for OCT, named label-free optical angiography, is reviewed (cf. Sec. 4). Some of the above-mentioned contrast enhancement OCT extensions are targeted to enable OCT molecular and biochemical sensitivity (prerequisite 4) as well as localized (quantitative) functional tissue information (prerequisite 5), with the most successful one being Doppler OCT. Though having been improved in many aspects, OCT so far is still not sensitive enough to provide absorption contrast or biochemical and molecular information. Therefore, multimodal optical imaging modalities with OCT incorporated have become a hot research topic. In this paper, the following combinations are reviewed: OCT with multiphoton tomography (MPT, for subcellular resolution); OCT with nonlinear microscopy (for label-free molecular tissue information, cf. Sec. 5.1); and OCT with photoacoustic imaging (for enhanced absorption sensitivity and penetration depth—prerequisite 6, cf. Sec. 5.2). Previous reviews of OCT focused on advanced screening in the fields of primary care,53 microscopy,54 rapid tissue screening,55 phantoms,56 high speed,57 and translational research,58 while recent application-specific OCT reviews covered ophthalmology,59–61 cardiology,62–66 dermatology,67–70 novel applications in pulmonary medicine,71 cancer,72 and optical coherence elastography,73 as well as OCT post- and signal processing.74,75 This review focuses on high-speed technology (SS light technology and parallelization of OCT detection), label-free angiography, and multimodal OCT.