What is the relationship between microtubules and spindle fibers in cell division?

Microtubules are the building blocks of spindle fibers, which are essential for cell division. During cell division, microtubules form the spindle fibers that help separate chromosomes and ensure each new cell receives the correct number of chromosomes. In summary, microtubules are the structural components of spindle fibers that play a crucial role in the process of cell division.