Best Answer: 
It was a novel-idea that came to him when he accompanied a Doctor who went to attend to a sick Child & used a "Liquid Crystal" strip containing this ingredient which was placed on the Child's forehead to get an approximate reading of his/her temperature. "Marvin Wernick" observed the different color-changes occurring due to temperature & that is when the idea came to him of a novel-product that could be designed in the form of a jewelry-piece which could then be said to indicate a specific "Mood" based on the "Color" displayed at any given time when worn. He then set about making some jewelry-items & eventually put a product together, then marketed it. However, he did not patent his invention which then left the door open for other entrepreneurs, who came along afterwards with their version(s) of "The Mood Ring" & "The Mood Chart", to get in on the marketability of the product, along with its profits.
Source(s):
Although I don't usually recommend "The Wikipedia" as a reference because of their policy that any registered member can edit any Web-page, which gives opportunity to misinformation &/or tampering of the Web-site, there is an E-article on "Mood Rings" there. I would also suggest going on Google & keying in "Mood Ring(s)" & "Marvin Wernick", which should bring a number of Web-sites up on this topic.
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