Brain Tonic was a drink aimed at children and produced by the company Goruda in 21st century Japan. It played a vital part in Axos' failed invasion of Earth. It was believed that it made the children more intelligent; however, in reality, it was bestowing upon the children a subconscious type of telepathy. This meant that any information a consumer learnt was passed on to the others, like a psychic gestalt.
The drink also contained a "chameleon molecule" which caused it to appear as plain water under any type of analysis. This molecule could also absorb energy and use it to change living tissue; this was used to transform human children into Axons. (COMIC: The Golden Ones)