This paper has shown how XML (extensible Markup Language) can be used to mark up content. Since XML documents, with meaningful tags, can be interpreted easily by humans as well as computers, they are ideal for the interchange of information. Because XML tags can be defined by an individual or organization, XML documents have proven useful in a variety of areas including chemistry, mathematics, music, literature, graphics, eCommerce and educational technology. This paper demonstrated a simple example of how XML could be used for developing eLearning applications where the content and presentation software can be separated from one another. This separation facilitates the maintenance, reuse and repurposing of both the content and the presentation software. (Contains 11 figures.)