This is a picture of the internal structure. Picture A and B come from Scaning Eletron Microscopy (SEM). It was found that A picture has a length of fibers uneven, and somewhat shorter than the picture B.
Next, Picture C and D come from Tranmission Electron Microscope (TEM). Found that the picture D will be darker than the picture C because the structure is coated with carbon, therefore has a strong.