Polyominoes

Joseph Myers and John Berglund found a polyhex that must be placed in two different ways in a tiling of a plane, such that one placement occurs twice as often as the other.

Tiling a square without cutting it into two.(Problem of the week 826, Spring 1997)

Polyform puzzle lessons for math educators to use with their students, including polyominoes, supertangrams, and polyarcs.