Moving beyond either total internal reflection fluorescence (TIRF) microscopy or static electron microscopy, they used a “correlative light and EM (CLEM) approach.” This meant the investigators would have the spatiotemporal resolution required for the study of IFT chains, which move at about three micrometers per second. A Chlamydomonas cell was quickly fixed during time-lapse photography of fluorescently labeled IFT trains. Following that, the cell was subjected to electron tomography to allow visualization of the way each train interacted with the microtubule. They also used movies obtained from light microscopy to add more detail to their findings.
To check the accuracy of their findings, they repeated their CLEM technique directly on cross-sections of the cilium itself. Indeed, they were then able to see the connections between the retrograde IFT trains and the A-microtubules, and between the anterograde IFT trains and the B-microtubules, confirming the directional specificity of the doublet structure.