Scientific explanations can in all kinds of forms: spoken, written, a demonstration. But sometimes the best words for the job are actually pictures.
Tell us (and show us!) in the comments about a picture — whether an infographic, photograph, data visualization, or a sketch — that made you finally understand a scientific concept. Be sure to explain just what the idea in question was and how the picture made it click into place.
Image: Every discovered Kepler planet as of 2013 / NASA.