Neuronal cell types identified in the Drosophila medulla. Cell types are organized according to: i) their expression of a TF-Gal4 (ap-, ey- and dll-Gal4 lines), ii) Columnar (C) vs. non-columnar (NC) cells and iii) presence of one dendritic arbor contacting R7 or R8 (R7/8), two arbors (R7 & R8) or ramifications in the lower medulla layers (LM). Numbers between parentheses represent the number of cells examined for each cell type. P&Y: pale and yellow ommatidia; OT: optic tubercle and Lo: lobula. New cell types are shown in red. Cell for which we describe a specific Gal4 enhancer trap line are noted in blue.