If Escher had worked for 3M, he may have designed something like this. The Block Memo is actually Japanese design studio Nendo's answer to the bank of Post-it notes on your desk: a three-sided block of sticky notes that can be peeled off from every side, and looks almost like an optical illusion when viewed from above.
Although as rectangular as any other block of notes, the Block Memo is actually made up of three different types of stickies. One face is taken up by large, square notes; on an adjoining side, half of this area is made up of medium sticky rectangles. On a third side, half of this area is devoted to even smaller sticky notes. Though it looks cubic from the top, the final side is made up of inverted shapes that let it sit on any desk with one corner pointing to the sky, like a 3-D tetromino.
The Block Memo is being sold in Japan for around $21, alongside another Nendo stationery design, a pair of notebooks called U-Note and Sa-Note. Intuitive, artistic designers can adopt the U-Note, which with pages that gradually fade from lined to unlined. Logical, left-brained thinkers can adopt the Sa-Note notebook, which has extra lines per page. Those are also available in Japan, for around $4 each.