The exclusion zone is a large stratum (typically on the order of a few microns to a millimeter) observed in pure liquid water, from which particles of other materials in suspension are repelled. It is observed next to the surface of solid materials, e.g. the walls of the container in which the liquid water is held, or solid specimens immersed in it, and also at the water/air interface.  Several independent research groups have reported observations of the exclusion zone next to hydrophilic surfaces. Some research groups have reported the observation of the exclusion zone next to metal surfaces. The Exclusion zone has been observed using different techniques, e.g. birefringence, neutron radiography, nuclear magnetic resonance, and others, and it has potentially high importance in biology, and in engineering applications such as filtration and microfluidics.