In this article the discovery of the superconductivity at39K in MgB2 is discussed in a didactic and conceptual way. To point out its importance the history of the superconductors is discribed shortly, from its discovery in 1911 in Hg up to nowadays. The main inherent characteristics to the superconductor state are pointed out and some of its applications are indicated and represented in illustrations. The text present then the changes that the MgB2 discovery brings to research and applications. In the way it is written, it is believed the text is of interest not only to the general scientific community, not specialized in superconductivity, but especially to high school physics teachers, that could take advantage of the text in activities involving topics of contemporary physics.
