Main Page | See live article | Alphabetical index A test tube is a kind of laboratory glassware, composed of a fingerlike length of glass tubing, open at the top, usually with a rounded lip at the top, and a rounded 'U' shaped bottom. They range in size from a couple inches to several inches long, from a few millimeters to a couple centimeters in diameter. They are designed to allow easy heating of samples, to be held in a flame, and often are made of expansion resistant glasses, such as Pyrex ®. Tests tubes are often preferred above beakers when multiple small chemical or biological samples have to be handled and/or stored. Vacutainers are a type of test tube that can be used for both collection and storage of blood. See also: In vitro This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.