How does an image become an icon?

"Jesus Christ was originally depicted without a beard. The heart symbol didn’t get its two round lobes until the 1400s, and the Coca-Cola bottle hasn’t changed in almost a century.
These are just a few of the interesting facts that Oxford University professor Martin Kemp encountered in the process of researching his latest project, Christ to Coke: How Image Becomes Icon. The book, which will be released Nov. 10, examines the stories behind the most famous pictures in the world."
Images from Martin Kemp’s book Christ to Coke: How does an image become an icon? - Slate Magazine