Figure 1. The appearance of the 72 hpf zebrafish with millimeter ruler, at magnification, and as observed by SD-OCT provided for appreciation of its small size. Zebrafish embryos were embedded in 1% agarose gel in an inverted microscopy Petri dish (A, B; B shows a magnified region of A). Embryos were scanned in three dimensions (3D), and reflectance of internal structures quantified. C-mode sections of the 3D data set could be isolated and tissue reflectance within a slice is displayed (C).