Fig. A dendritic growth cone extends from the tip of a growing dendrite (D). The growth cone consists of an enlargement filled with a dark, granular cytoplasm characteristic of a dense actin matrix. Filopodia (arrows) extend from the enlargement. A region inside the growth cone (asterisk) is filled with numerous large vesicles. Large amounts of extracellular space (ES) are apparent. Scale = 1 µm. (1 day-old rat, hippocampus area CA1.)