Wilson A. Bentley, an American naturalist, studied precipitation whenever he could spare a few moments away from his dairy farm. Rain, sleet, hail, snow—it made little difference—Bentley simply loved precipitation! Almost a century ago he developed an ingenious method for measuring the size of raindrops. This article describes a lesson that provides students with the opportunity to learn to measure the number, size, and shape of raindrops, and determine the rate of rainfall—just like Bentley did.