In this chapter, the innovators and extreme innovators are discussed. These types of consumers are very important because they grow the infant market. The extreme innovators purchase an incomplete product at high price and contribute to the product development. Then the innovators purchase an immature product at a relatively high price and their reviews have great effects on the future diffusion. We also follow their second and later purchases because their behavior in repeat purchases has a strong relation with the alternation of product generations. In other words, they are the motive power for the alternation of products or the change to the alternative products.