Tesselations and Fractals

A tessellation or tiling is the covering of a surface, often a plane, using one or more geometric shapes, called tiles, with no overlaps and no gaps.

Shodor Interactives

http://www.shodor.org/interactivate/activities/Tessellate/

Theoretical fractals are infinitely self-similar iterated and detailed mathematical constructs, of which many examples have been formulated and studied