In 1992 Elon Kohlberg, a professor at the Harvard Business School, learned for himself just how hard it is to teach place value concepts to children. While trying to help his young nephew, Elon recognized what elementary school teachers have long known, that he needed a physical model for our number system. He began with pebbles and plastic boxes, created some games and activities to use with them, and was elated to see how helpful they were to his nephew.

Two years later, Elon brought the materials out again for his young son, who insisted on taking them to “show and tell” at his school. His son’s teacher was so impressed with the activities that she prodded Elon to develop a teaching model for use in all classrooms.

Thinking about what would be required to make the model truly useful to teachers and children everywhere, Elon identified two key features. The boxes should be constructed to hold at most ten pebbles and to close only when full; and there should be larger boxes, representing hundreds, each capable of holding ten of the original boxes. But despite brainstorming with a number of professional designers, Elon could not see how to build such a model without making it hopelessly complex, and so he gave up.

A few years later, and for no apparent reason, the missing idea suddenly occurred to him: Everything would fall into place if only the box looked just like a pebble! After all, he reasoned, isn’t this the fundamental idea of base ten, that ten is again a “one,” only bigger? By the spring of 1997, and with the help of the award-winning design firm IDEO, Elon had an elegant product. Our blocks can now be found in over 10,000 classrooms!