If you enter the terms "Albert Einstein" and "compounding" into an Internet search engine, you'll discover a wide variety of quotes attributed to the great inventor. Some results say Einstein called compounding the "greatest mathematical discovery of all time," while others say he called it the "most powerful force in the universe." Despite the many variations, Einstein's point is valid: compounding can add fuel to your portfolio's growth. The key is to allow enough time to let it go to work.