Evan Minto notes that flexible grids created with CSS Grid’s repeat, auto-fill, and minmax are only intrinsically responsive (responsive to their container rather than the viewport) up to a point, because when the container width is narrower than the minimum width specified in minmax the grid children overflow.
Applying media queries to the grid is not a satisfactory solution because they relate to the the viewport (hence why Every Layout often prefer Flexbox to CSS Grid because it allows them to achieve intrinsic responsiveness).
However we’ll soon be able to suggest grid item width as a percentage of the parent container, avoiding the overflow problem. The new “CSS Math functions” to help us achieve this are min(), max() and clamp(). At the time of writing, these are only supported in Safari however Chrome support is in the pipeline.