Metatron's Cube is a modern New Age name for a geometric figure composed of 13 equal circles with lines from the center of each circle extending out to the centers of the other 12 circles. Some New Age teachers call a variant of this figure the Fruit of Life.
The name of Metatron's Cube makes reference to Metatron, an angel mentioned in apocryphal texts including the Second Book of Enoch and the Book of the Palaces. These texts rank Metatron second only to the Abrahamic God in the hierarchy of spiritual beings. The derivation of Metatron's cube from the tree of life, which the Talmud clearly states was excluded from human experience during the exile from Eden, has led some scholars (including Johann Andreas Eisenmenger) to portray Metatron as the means by which humanity was given knowledge of YHVH; presumably implying that study of Metatron's cube would be necessary to understanding the tree of life.
The pattern delineated by many of the lines can be created by orthographic projections of the first three Platonic solids. Specifically, the line pattern includes projections of a double tetrahedron (aka stellated octahedron), a cube within a cube (a three dimensional projection of a tesseract), and an octahedron. Although the image below shows the dodecahedron and the icosahedron fitting the pattern of Metatron's Cube, the vertices of those shapes do not coincide with the centers of the 13 circles (the icosahedron projection in the image below is false).
See also 
- http://originalburn.com/knickknacks/metatrons_cube_graph - animated creation of Metatron's cube using PaperJS
- A. Orlov, The Enoch-Metatron Tradition (Tuebingen: Mohr-Siebeck, 2005) 148-208; http://www.scribd.com/doc/2024701/Hebrew-book-of-3-Enoch.