The morphology of healthy and pathological human brain tissue, as well as the brain structural organization of various animal models has been imaged in-vitro using ultrahigh resolution optical coherence tomography (UHR OCT). Micrometer-scale OCT resolution (< 2 μm axial resolution) was achieved at different central wavelengths by interfacing three state-of-the-art broad bandwidth light sources (Ti:Al2O3, λc = 790 nm, Δλ = 260 nm and Pout = 50 mW; PCF based laser, λc = 1150 nm, Δλ = 350 nm and Pout = 2 W; Fiber laser based light source, λc = 1350 nm, Δλ = 470 nm and Pout = 4 mW) to a modular free-space OCT system, utilizing a dynamic focusing and designed for optimal performance in the appropriate wavelength regions. Images acquired from a fixed honeybee brain demonstrated the ability of UHR OCT to image the globular structure of the brain, some fine morphological details such as the nerve fiber bundles connecting the medulla (visual center) to the honeybee eyes, and the interfaces
between different tissue layers in the medulla. Tomograms of various human neuropathologies demonstrated the feasibility of UHR OCT to visualize morphological details such as small (~20 μm) calcifications typical for fibrous meningioma, and enlarged nuclei of cancer cells (~10-15 μm) characteristic for many other neuropathologies. In addition UHR OCT was used to image cellular morphology in living ganglion cells.