Visual perception, an interesting and popular research focus of psychology, is the function of the eyes and brain working together to interpret our surroundings. Take this picture for example: some people may see a vase, while others may see two faces. Perhaps if you look at it long enough you will see both. This phenomenon relates to the theory of figure-ground organization. Figure-ground organization is one principle of Gesalt's theories of perceptual organization. This concept explains that when we look at an object we do not just look at the object; instead, we see the object in relation to its background. This explains why reversible figure-ground images, like the one above, can change in our mind as we look at it.
I find perception to be a very interesting topic because it gives a biological example of how differently everyone interprets information. Reversible images in general are a classic illustration of how every aspect of life can have more than one dimension, more than one point of view. Although figure-ground perception deals specifically with sensory information, in many ways it represents how people all have different perceptions of the world--different ideas, opinions and views--and that these can all change over time.