Microtubules are one of the three basic components of the cytoskeleton and also function in the movement of other organelles throughout the cytoplasm. The dynamic biopolymers are composed of two closely related globular subunits known as alpha-tubulin and beta-tubulin bound together into heterodimers. The subunits of microtubules are further organized into 13 parallel protofilaments organized in such a way that structure is polarized. In the digital video sequences appearing in this section, the proximity between the expansive intracellular microtubule network (labeled with a mEmerald-EB3 fusion) and the nucleus (visualized with mCherry fused to H2B) is demonstrated.