This study on the zebrafish optic tectum is a series of four images with magnifications ranging from the SEM block face overview to of the zebrafish head to high magnification (80,000X) showing optic tectum synapse. The first image is a bloc face SEM image at 200x of the epon embedded zebrafish head. This image, the second image in the series, is another block face SEM low magnification image of the tectum. The third image is a 60,000X TEM image of a OTO fixation and copper lead en bloc staining of zebrafish optic tectum synapse. The fourth image is a 80,000X TEM image of a zebrafish optic tectum synapse. This low magnification image larval zebrafish image of the optic tectum was collected on a Gatan 3View® serial block face scanning electron microscope (SBFSEM). The 3View® is attached to a FEI Quanta 600 FEG SEM. Block face imaging is a way to look at epon embedded specimens using backscattered electrons in the SEM. A diamond knife in the vacuum chamber of the SEM cuts hundreds of ultrathin serial sections, thus gathering a perfected registered stack of images. Reference for SBFSEM: Denk, W. and H. Horstmann. Serial block face scanning electron microscopy to reconstruct three- dimensional tissue nanostructure. PloS Biology vol 2, 11; e329 doi:10.1371/journal.pbio.0020329 Microwave processing, osmium tetroxoxide/osmid procedure for enhancing membranes, and copper lead en bloc staining. Procedure for specimen preparation available at http://www.stanford.edu/~redhair/JoAnn_Buchanan.