This paper presents a comprehensive analysis of direct current (DC) microgrids in the context of the rural energy internet, addressing the demand for sustainable, reliable, and efficient energy solutions in rural communities. We discuss the motivations for developing DC microgrids in the rural energy internet, including energy access and equity, environmental sustainability, economic growth, and advancements in microgrid technology. We explore the basic structure of DC microgrids, emphasizing key components such as photovoltaic sources, electrochemical storage systems, public grid connection, and user loads. We also explore the value of DC microgrids in the rural energy internet, highlighting their benefits in enhancing energy efficiency, improving compatibility with renewable energy and energy storage systems, scalability and modularity, reducing infrastructure costs, and empowering local communities through distributed energy systems. Finally, the paper evaluates the potential impact of DC microgrid research on the development of the rural energy internet, and discusses the challenges and future research directions for DC microgrids in rural applications.