Renoir: Two Sisters (1881). Tile 1
Artist: Pierre-Auguste Renoir French, 1841 - 1919
Dimensions: 100.5 cm × 81 cm (39.6 in × 32 in)
Medium: Oil on canvas
Location: Art Institute of Chicago
Style: Impressionism.
Two Sisters or On the Terrace is an 1881 oil-on-canvas painting by French artist Pierre-Auguste Renoir. The title Two Sisters  was given to the painting by Renoir, and the title On the Terrace by its first owner Paul Durand-Ruel. The painting shows a seated girl ("the elder sister"), next to which is a little girl ("the younger sister"), who looks directly at the viewer. Source: Wikipedia: Two Sisters (On the Terrace)

Golden rectangle
A golden rectangle is a rectangle whose side lengths are in the golden ratio, one-to-phi, that is, approximately 1:1.618. A distinctive feature of this shape is that when a square section is removed, the remainder is another golden rectangle, that is, with the same proportions as the first. Square removal can be repeated infinitely, which leads to an approximation of the golden or Fibonacci spiral.

Droste Effect
The Droste effect is a specific kind of recursive picture, one that in heraldry is termed mise en abyme. An image exhibiting the Droste effect depicts a smaller version of itself in a place where a similar picture would realistically be expected to appear. This smaller version then depicts an even smaller version of itself in the same place, and so on. Only in theory could this go on forever; practically, it continues only as long as the resolution of the picture allows, which is relatively short, since each iteration geometrically reduces the picture's size. It is a visual example of a strange loop, a self-referential system of instancing which is the cornerstone of fractal geometry. Source: Wikipedia, Droste Effect.