The mitotic spindle is the complex machinery that enables a cell to segregate its genetic material faithfully. Without fidelity in this process, genetic abnormalities may occur which, in turn, can lead to cancer. Microtubules of the mitotic spindle are bundled together to form kinetochore fibres which contribute to the movement of replicated chromosomes during cell division, helping to ensure the DNA is equally divided. Electron microscopy has long been used to observe inter-microtubule bridges within kinetochore fibres and, although they are thought to confer stability to the fibres thus ensuring faithful mitosis, their identity and function is yet to be fully established. These inter-microtubule cross-linkers were thought to be simple structures, providing a bridge directly between two microtubules. Here, three dimensional electron microscopy was used to examine these cross-linkers in unprecedented detail - revealing a complex network of microtubule connectors which we have termed 'the mesh'. To establish the functional role of the mesh, levels of a known microtubule crosslinker, the TACC3-chTOG-clathrin complex, were manipulated. In cells with too much mesh, kinetochore microtubules were found to be disorganised - forming tighter clusters within fibres and deviating from their parallel trajectories. Kinetochore fibres were also found to contain more microtubules than in control cells, and took longer to complete mitosis. These observations provide evidence that the mesh plays a functional role in the organisation within kinetochore fibres, directly impacting the ability of the cell to divide successfully. In addition to fine kinetochore fibre structure, scanning electron microscopy was optimised to examine changes to the whole spindle structure after manipulation of the mesh. This revealed changes to spindle architecture when microtubuleassociated proteins were altered, and offers insight into how cancer can be initiated when these proteins are dysregulated.