A plastic embedding technique employing fluorescently labelled dextran-amines is described. After application of tracer to cut nerves and appropriate transport time, animals were fixed in paraformaldehyde. Subsequently their brains were dissected, heads and brains were dehydrated, embedded in methacrylate and sectioned serially on a rotary microtome. Plastic sections allow high resolution of single neuron profiles and complete serial reconstruction of undistorted sections, including embryos with large amounts of yolk. In conjunction with whole mount analysis and double labelling, this technique can accurately reveal the spatial relationships of nerve components throughout development.