Abstract
During cell division, the network of microtubules undergoes massive rearrangement to self-organize into the spindle, a bipolar structure essential for accurate chromosome segregation. This structure ensures the stable transmission of the genome from the mother cell to two daughter cells, yet the process by which the ordered architecture emerges from a collection of protein "parts" remains a mystery. In this review, we focus on several key spindle proteins, describing how they move, crosslink, and grow microtubules in vitro and contribute to the spindle's structural organization. We categorize these proteins into groups, such as transporters, bundlers, and nucleators, to highlight their functional roles. We also present an advanced perspective on the spindle's complex polymer architecture and its temporal assembly order in cellular contexts. This in situ level information should guide the minimal reconstitution of the spindle, helping to elucidate the biophysical principles underlying essential cytoskeletal self-organization.