CSS Subgrid is a significant advancement in web design, introduced in Level 2 of the CSS Grid specification to address the limitations of nested grids in Level 1. CSS Grids and Flexbox have been essential tools for creating grid-based layouts, but they struggled with nested structures, where elements within a grid acted independently, causing management and responsiveness issues. Subgrids solve these problems by allowing nested grids that maintain predictable behavior and alignment with the parent grid, enhancing responsiveness across different devices. Despite their advantages, subgrid implementation remains limited, with only a few browsers like Mozilla Firefox supporting it extensively. This feature is particularly useful for developers seeking to create scalable and aesthetically pleasing web designs without needing complex workarounds or additional code.