3, the use of three lines to denote the number 3 occurred in many ancient writing systems. In cursive script the three strokes were eventually connected to form the modern representation of the digit.
X, the earliest known use of X to represent multiplication was used by the Scottish mathematician John Napier, in his 1618 paper that first described the logarithm.
3X3 is an online gallery of 9 images that are replaced every month. The name is a numerical nod to the classic square shape of Instagram posts.