The classes `flex items-center justify-center` are used for centering. `justify-center` handles horizontal centering. `items-center` handles vertical centering. The "Gotcha" is that `items-center` needs the parent container to have a defined height for vertical centering to work as expected.
In this example, the orange parent container below does not have an explicit height (e.g., `h-32`). Its height is determined solely by its content. Therefore, `items-center` will vertically align the child within that content-derived height, which might not look "centered" if you expect it to fill a larger implicit space.
Notice how the "Child Item" is horizontally centered, but it appears at the top of any conceptual larger vertical space because the parent `div` (bg-orange-200) only grew tall enough to contain its child plus its own padding.
Here, the teal parent container has an explicit height class (`h-48`). Now, `items-center` can correctly vertically center the child within this defined 48-unit height.
The "Centered Child" is now perfectly centered both horizontally and vertically within its parent because the parent has a defined height (`h-48`).