Flagella staining:

Flagella is extremely thin tail like structure of bacteria used for motility. It is so thin that it requires special stain to be seen under microscope.

Flagellar staining is important to distinguish between flagellar and non-flagellar organism, to count the number of flagella and to know their arrangement pattern.

Mordant, usually tannic acid is used to coat and thicken the flagella. Then the stain is added(parasaniline or basic fuchsin). Flagella being so fragile, no heat fixing or blotting is done during the process.