Volcanic eruptions have the diversities in the time scales within 4.6 GA of the Earth’s age, the magnitude of eruptive volume, the style (how magmas erupt). Together with these, the tectonic setting where a volcano locates and the chemical compositions of magmas characterize the eruption. The complexity resulting from these diversities make it difficult to share our recognitions and interests on volcanic eruptions. Before learning the fundamental processes such as vesiculation and crystallization of magmas in volcanic eruptions, we need to have our common recognitions and interests to share for scientific approaches. In this chapter, I will show specific examples of eruptions to share the scientific interests for latter chapters.