Why do we stain cells while observing under microscope

Why do we stain cells while observing

under microscope? List commonly used stains. 

Stains help us visualise specific organelles of cells in better way. Otherwise these organelles are not easily recognisable  via microscope. Stains

or dyes are basic or acidic in nature have affinity to certain organelles.  

For example, methylene blue is

a basic dye which has affinity to nucleic acid and hence it can stain nucleus. 

Methylene blue is commonly used to stain animal cells. Similarly, iodine dye is used to detect starch and used to stain

plant cells. Eosin is used to identify RBCs, cell membrane and cytoplasm. 

Safarnin is another nuclear stain, and also used to stain Rheo leaves to visualize stomata.