What the classical Golgi looks like. (a) Top: an electron micrograph of a section through a typical metazoan cell. The Golgi is a stack of cisternae arranged from cis (light green) to trans (dark green). Note the contact sites between the trans cisternae and ER (Caenorhabditis elegans hypodermal cells courtesy of Gillian Howard (MRC-LMB); scale bar = 500 nm). Bottom: a schematic drawing of the electron micrograph on the left, with the important structures labeled: the cis-Golgi is colored pale green, the trans-Golgi dark green. (b) A Golgi from the unicellular green alga Ostreococcus tauri imaged by electron cryotomography. The sample is frozen rather than fixed and so this represents one of the first images of a native Golgi stack. Left: a single slice through the three-dimensional reconstruction. Right: the Golgi highlighted in a view through the whole cell: cisternae are colored purple, red, gold, yellow, and green (cis to trans), and ER light blue. From Henderson et al. (2007), PLoS One 2, e749; scale bars = 100 nm.