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A basic characteristic of biological tissue is that water molecules move through and within it, by a process called diffusion. Some materials have the interesting property that diffusion happens faster in some direction than in others. I'm demonstrating that here with some scans of inkblots that I made in two kinds of materials: kleenex, and newspaper. In kleenex- the ink spreads at same rate in all directions, but newspaper has a preferred direction where the ink moves faster. The name for this phenemon is anisotropy. The wider the variation in diffusion rate as a function of direction, the more a anisotropic a material is. This one-dimensional family of ellipses represents some of the different levels of anisotropy which can occur in two dimensions.