Flexbox for most stuff, resort to grid only if flexbox can't solve your layout. The way I see it, if there is horizontal or vertical stacking, it's flexbox. An

Flexbox for most stuff, resort to grid only if flexbox can't solve your layout. The way I see it, if there is horizontal or vertical stacking, it's flexbox. And since you can nest, it covers a wide ranged of typical layout patterns (boxes within boxes). One caveat, since flexbox only arranges vertically or horizontally, you have to insert container flex elements, which means it affects the markup, so you are a bit constrained if you want to make it really responsive and rearrange everything based on viewport size. Grid is more complex, and useful for fixed layouts when things have to align more. With sub-grid support it will be even more powerful.