# Tailwind CSS
## FAQ
┌ How to Apply Classes Via CSS
Use [@apply](https://tailwindcss.com/docs/functions-and-directives#apply=).
```css
@tailwind base;
@tailwind components;
@tailwind utilities;
@layer base {
h1 {
@apply text-2xl;
}
h2 {
@apply text-xl;
}
}
@layer components {
.btn-blue {
@apply bg-blue-500 hover:bg-blue-700 text-white font-bold py-2 px-4 rounded;
}
}
@layer utilities {
.filter-none {
filter: none;
}
.filter-grayscale {
filter: grayscale(100%);
}
}
```
See also other methods to [reuse styles](https://tailwindcss.com/docs/reusing-styles).