Reptiles (1943). The life cycle of a little alligator. Amid all kinds of objects, a drawing book lies open, and the drawing on view is a mosaic of reptilian figures in three contrasting shades. Evidently one of them has tired of laying flat and rigid amongst his fellows, so he puts one plastic-looking leg over the edge of the book, wrenches himself free and launches out into real life. He climbs up the back of a book on zoology and works his way up the slippery slope of a set square to the highest point of his existence. Then after a quick snort, tired but fulfilled, he goes downhill again, via an ashtray, to the level surface, to that flat drawing paper, and meekly rejoins his erst while friends, taking up once more his function as an element of surface division.

Encounter (1944). Out from the gray surface of a back wall there develops a complicated pattern of white and black figures of little men. And since men who desire to live need at least a floor to walk on, a floor has been designed for them, with a circular gap in the middle so that as much as possible can still be seen of the back wall. In this way they are forced, not only to walk in a ring, but also to meet each other in the foreground: a white optimist and a black pessimist shaking hands with one another.

Other World (1947). Escher constructed a five-sided chamber in which all sides are interchangeable. This is his first print to focus primarily on his idea of relativity, how one object is seen in relation to another. The Islamic figurine of a harpy, a mythical creature with a bird's body and a human head, was a gift from Escher's father-in-law and appears in several of his prints.
  The trick to seeing the different perception points in this picture is to look at the birds in the windows. If you look at the bird on the top of the picture you see that you are looking down on the room. If you look at the bird on the bottom or the picture you realize that you are now looking up at the room. If you look at the bird in the middle of the picture you see that you are simply looking into the room. What Escher did in this picture is change the points at which the focus terminates from the zenith to the nadir.

High & Low (X-eyed view) (1947). Now this picture incorporates the same concepts as "Other World" does; in the top portion of the picture you are looking down on the landscape and building, and in the bottom portion you are looking at the landscape from ground level. To do this piece Escher had to take into account the horizon, the nadir, and the zenith, and manipulate them all to form a picture that flowed and made sense.

Drawing Hands (1948). A piece of paper is fixed to a base with drawing pins. A right hand is busy sketching a shirt-cuff upon this drawing paper. At this point its work is incomplete, but a little further to the right it has already drawn a left hand emerging from a sleeve in such detail that this hand has come right up out of the flat surface, and in its turn it is sketching the cuff from which the right hand is emerging, as though it were a living member.

Bond of Union (1956). Two spirals merge and portray, on the left, the head of a woman and, on the right, that of a man. As an endless band, their foreheads intertwined, they form a double unity. The suggestion of space is magnified by spheres which float in front of, within and behind the hollow images.

Ascending/Descending (1960). The endless stairs which are the main motif of this picture were taken from an article by L.S. and Roger Penrose in the February, 1958 issue of the British Journal of Psychology. A rectangular inner courtyard is bounded by a building that is roofed in by a never ending stairway. The inhabitants of these living-quarters would appear to be monks, adherents of some unknown sect. Perhaps it is their ritual duty to climb those stairs for a few hours each day. It would seem that when they get tired they are allowed to turn about and go downstairs instead of up. Yet both directions, though not without meaning, are totally useless. Two recalcitrant individuals refuse,for the time being, to take any part in this exercise. They have no use for it at all, but no doubt sooner or later they will be brought to see the error of their nonconformity.