Human beings use threes to conceptualize everything. Three data points are enough to describe an entire set. Take time for example. We break it into before, during, and after. Look at the basic structure of color.
For example, primary colors in pigment (red, yellow, & blue) make up all colors. Color is also classified into primary, secondary, and tertiary. Look at our basic sentence structure to communicate. Subject, verb, object. In Japan the ordering is subject, object, verb, but they both utilize three components to communicate. The list goes on and on and on. . .
This section includes three videos and three songs of Three is the Magic Number. This includes songs and videos by School House Rock, Blind Melon and De La Soul. We also include a featured article by the late Professor Alan Dundees on the number three in American culture. This section concludes with an interview with Zip FM, Tokyo, Japan by Michael S Eck, author of 
For about 30 years, Michael Eck has been thinking about threes. Things that come in threes. Now he combines that esoteric interest with his attachment to the Internet by creating what he hopes will be the book with the most authors ever (a lot more than three, anyway).
He suggests that in our minds we break concepts into three parts to understand whatever it is we are thinking about. We use threes to define systems. We use the third or middle point with regard to the extremes to define a point of view. Yadda yadda yadda.
The concept is simple. Just think of something that comes in threes, then go to this site and contribute it. For example: the colors on the American flag; Caesar’s most famous words, “Veni, vidi, vici” (“I came, I saw, I conquered”); the number of legs on each side of an insect.