(A) Confocal microscopic image of a 3-day-old larva stained with an anti-acetylated tubulin antibody to label neurites and cilia. Anatomical landmarks are labeled. (B) Blender visualization of all photoreceptor cells and all synapses of the minimal eye circuit shown in relation to the outline of neuropil, reconstructed by ssTEM. The position of synapses in the visual circuit reveals the primary and secondary optic neuropils. The schematized ciliary band cells are also shown. (C) ssTEM reconstruction of photoreceptors, glia cells and synapses. (D) ssTEM reconstruction of photoreceptors and primary interneurons (IN1). (E) ssTEM reconstrucion showing the trans-optic-neuropil interneurons (INton) connecting the two optic neuropils. (F) Confocal microscopic image of a 3-day-old larva stained with phalloidin to label the musculature (red) and with DAPI to label nuclei (cyan). (G) ssTEM reconstruction of muscles and motorneurons (MN). (H) ssTEM reconstruction of the complete cell complement of the minimal visual circuit. Neurons are colored by type. Pigment cups are shown in brown. All images show anterior views. PRC, photoreceptor; IN, interneuron; MN, motorneuron; eyeal, anterior-left eye; eyear, anterior-right eye; eyepl, posterior-left eye; eyepr, posterior-right eye; ON, optic neuropil; cPRC, ciliary photoreceptor; DCC, dorsal branch of the circumesophageal connectives; VCC, ventral branch of the circumesophageal connectives; NSP, neurosecretory plexus; DLM, dorsal longitudinal muscle; VLM, ventral longitudinal muscle. The coloring of cell types is consistent throughout the paper (PRC, blue; IN1, yellow; INint, lilac; INton , magenta; INdc, light brown; INvc, cian; INsn, green; MN, red). Scale bars, 30 µm. The Blender atlas with the volume rendering of all cells and synapses is available in Randel et al. (2014).