A test tube with a stopper is often used for temporary storage of chemical or biological samples.
Test tubes are usually held in special-purpose racks, clamps, or tongs. Some racks for culture tubes are designed to hold the tubes in a nearly horizontal position, so as to maximize the surface of the culture medium inside.
Test tubes are sometimes put to casual uses outside of lab environments, e.g. as flower vases, glassware for certain weak shots, or containers for spices.
Where large numbers of tests are run or only small amounts are available for testing, or both, microtiter plates are often used as small test tubes.