Final answer:
Negative staining is the procedure in which no heat fixing or strong chemicals are used. Acidic dyes are used in negative staining to observe cells that appear clear or colorless against a dark background.
Step-by-step explanation:
The procedure in which no heat fixing or strong chemicals are used is negative staining. Negative staining is a staining technique that uses acidic dyes, such as India ink or nigrosin, which are repelled by the cells being observed. As a result, the cells will appear as clear or colorless against a dark background. Negative staining is often used to observe bacterial capsules or flagella, as well as structures that are difficult to visualize with other staining methods.