Markdown has revolutionized the way articles and text are written by simplifying content creation with its special syntax that converts easily into HTML, enabling developers to enhance their writing experience. Gatsby, a static site generator, supports Markdown, allowing for the seamless transformation of Markdown files into full-fledged web pages or blogs. This article demonstrates how to build a Markdown plugin for a Gatsby blog, specifically focusing on creating a text highlighting plugin that identifies and processes specified syntax into styled HTML. The process involves using the abstract syntax tree (AST) of Markdown files to hook into and modify the content with the help of gatsby-transformer-remark. Developers can leverage this tutorial to create and customize their own plugins, enhancing the functionality of their projects. Additionally, the article provides insights into setting up the environment, writing the plugin code, and testing it within a Gatsby project, ultimately allowing for greater flexibility and creativity in content presentation.