Objective:
Two objects are similar if we can turn them into the same shape by either stretching or shrinking (and sometimes rotating). Suppose there are many similar objects of different sizes. Now, if we can use the same stretching or shrinking to make them all similar, they are said to be self-similar. For instance, the family of ducks is similar but not self-similar because the ducklings are same.

On the other hand, the school of fish is self-similar because a uniform stretching or shrinking will make them all the same Here, the uniform stretching and shrinking is done by a scaling factor. Self-similar objects do not have beginning or ending, and they form an endless sequence. We build a Pythagoras tree by stacking self-similar house motifs on top of the right-angled equilateral triangle roofs.  Because of self-similarity, there are Pythagoras trees within a Pythagoras tree.

Scary words: similar, self-similarity, scaling factor, motif, Pythagoras tree.

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