Hoods are a common class of instrument, which act as a protective enclosure for various types of laboratory experiments. They serve to shield experimental samples from the environment, as well as to protect the researcher from hazardous or infectious samples. “The Hood” is a term that can include laminar flow benches, fume hoods, as well as tissue culture hoods or biosafety cabinets. All hoods operate based on the principle of laminar flow and have the same basic components, including a window sash and protective glass barrier, a non-porous work surface, and an air intake and exhaust. The type of hood used should be chosen based on the experiment. For example, fume hoods typically protect the user, and not the experimental environment. In contrast, laminar flow benches protect the experiment, but not the user, and therefore can but used to keep experimental samples sterile, when they pose no threat. If both the user and the experiment must be protected, a tissue culture hood or biosafety cabinet can be used. Tissue culture hoods maintain sterility of cell lines, while biosafety cabinets provide protection during procedures utilizing infectious agents Once the appropriate unit is chosen for an experiment, the user should wear appropriate protective equipment, and follow all necessary safety procedures. This video discusses the principle of laminar flow, how the hood is used, and discusses the different types of procedures that should be carried out in each type of hood.