3D Reconstruction means generally the method that reconstructs the original 3D structure from projection images or surface images of a 3D object.
Here, we talk about 3D Reconstruction Method by Transmission Electron Microscopy Methods. This technique is the same as CT(Computed Tomography) on the basis mathematical. In short, it is based on Central Slice Theorem that shows "Any projection image Fourier Transformed is one slice that pass through the origin on Fourier Space.".