From the Howard Hughes Medical Institute's extraordinary BioInteractive series comes EarthViewer: an interactive resource that allows science students to explore how the earth has changed from the Hadean Eon (approximately 4 - 4.6 billion years ago) through the present. EarthViewer may be best described as an interactive map and timeline. As users scroll across eons and eras, they can view geological and biological events emerge on a model of Earth. A toolbar along the bottom of EarthViewer allows users to view certain data points, such as oxygen levels, as a chart. Visitors can also select "In depth" in the toolbar, which offers helpful explanations about a variety of phenomena, including plate tectonics and the origin of eukaryotes. Science educators will also want to the check out the teacher's tab, which offers some ideas for incorporating EarthViewer into the classroom. Visitors may access EarthViewer online via Google Chrome (version 8 or newer) or Firefox (version 4 or newer). Alternatively, visitors may also download a version of EarthViewer available for Mac or Windows computers.