Contrary to appearances, Collective Intelligence is nothing obvious; to the point that we are confronted frequently with situations of "Collective stupidity". We can raise the following question: what makes something not working, while it should be so obvious? In other words, what does the notion of Collective Intelligence cover? By asking this question, we need to meet the Human Being, the main actor of our subject. This book analyses the development of Collective Intelligence by a better knowledge of the diversity of the temperaments and behavioural and relational processes. The purpose is to help the reader become a better Collective Intelligence Leader, who will be able to capitalize on the specificities and the differences of the individuals present in its collective, and transform these differences into complementarities, which are a source of wealth.