The major difference between SEM and Tem is?

Question

Microbiology

Answer 1

in SEM you look at either backscattered or secondary electrones
in TEM you look how much of your electron beam makes it through the sample onto your phosphor screen or film camera.
The resolution of the TEM is better.

Both other answers are correct too.
SEM is used for looking at the surface or at the atomic composition of it. If you want to look at the surface you may have to cover the surface by a very thin (couple of atoms) thick layer of gold.
TEM requires very thin sections (usually about 70nm thick) or very small structures. Biological tissue requires very good fixation and additional staining to see contrast.

Answer 2

I'm not the expert, but I think the big difference is that SEM is best at seeing the surface & TEM can see molecular differences inside the sample. TEM is transmission of the electron thru the sample & the electrons interact with the molecules while inside.

Answer 3

in SEM The specimen is scanned and then viewed but in TEM electrons pass thro d specimen(ie transmitted) and then viewed