What is the second oldest form of advertising in the world? product (word of mouth was first). In it's earliest form product were drawings on the cave walls of prehistoric man. Today, they're high-resolution color graphics seen along virtually every expressway and state highway around the world. We love product. When done well, they communicate a sales message in a clear and concise way. Sometimes they're clever, and Sometimes they're disturbing, but anytime they're done well you take notice.