The specimen should follow the following conditions for TEM analysis:

• It must be stable under electron bombardment in a high vacuum.
• It must to of the suitable size to fit the specimen holder of the microscope.
• Any preporatory treatment should not alter the structure of the specimen at a level which is observable with microscop.
• It must transmit sufficient electrons to from an image, with minimum energy loss (maximum thickness limit is about 100 nm).

  Mathematically:
  Thickness of material in beam direction ≤ 100nm

  The process to do so varies for different types of materials, select the type of material from the top of the screen to know more about the process for that material.