[blog] Introducing Pigment CSS blog post

docs/pages/blog/introducing-pigment-css.js

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+import * as React from 'react';
+import TopLayoutBlog from 'docs/src/modules/components/TopLayoutBlog';
+import { docs } from './introducing-pigment-css.md?muiMarkdown';
+
+export default function Page() {
+  return <TopLayoutBlog docs={docs} />;
+}

docs/pages/blog/introducing-pigment-css.md

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+---
+title: 'Introducing Pigment CSS: the next generation of CSS-in-JS for Material UI'
+description: 'Pigment CSS offers significant performance gains along with RSC and App Router support.'
+date: 2024-05-14T00:00:00.000Z
+authors: ['samuelsycamore']
+tags: ['Pigment CSS']
+card: false
+---
+
+In the era of React Server Components and the Next.js App Router, component libraries like Material UI must make some paradigm-shifting changes to reap the potential performance gains by moving more of the work of rendering UIs from run time to build time.
+
+Trouble is, the "traditional" CSS-in-JS solutions we rely on aren't able to come along with us because so much of what they do happens at run time.
+And with nearly 50% of respondents in the [State of CSS 2023 survey](https://2023.stateofcss.com/en-US/css-in-js/) indicating they use styled-components, we're looking at a whole lot of React developers with no clear path forward from here.
+
+For a library as widely used as Material UI, the biggest challenge is to stay up-to-date while introducing as few breaking changes as humanly possible, to maintain a consistent and reliable developer experience without asking users to completely change the way they build UI components.
+
+That's where Pigment CSS comes in.
+
+Pigment CSS is MUI's new in-house styling solution: a zero-runtime CSS-in-JS package that generates colocated styles to their own CSS files at build time.
+With Pigment CSS you get the latest and greatest advancements in CSS along with RSC compatibility, _plus_ significant performance improvements when compared with Emotion in Material UI v5.
+And though it's specially tailored to meet the needs of Material UI users, Pigment CSS can be used with _any_ React component library you prefer.
+
+## Why Pigment CSS?
+
+### Traditional CSS-in-JS is not enough
+
+Emotion made a lot of sense for Material UI v5 in late 2021, but so much has changed in the React ecosystem since then.
+In early 2023 React introduced Server Components, and Next.js offered the first implementation of the new spec with the App Router shortly thereafter.
+
+RSCs unlock a whole new realm of possibilities for React; for us as UI developers, it means we can create components that are fully rendered at build time so we don't have to pass that burden on to the client at run time.
+But working with RSCs requires us to let go of familiar APIs like `useContext`, which in turn becomes a major blocker for using the last generation's style engines like Emotion that rely heavily on this hook for theming.
+
+:::info
+To learn more about RSCs, we highly recommend reading [Making Sense of React Server Components](https://www.joshwcomeau.com/react/server-components/) by Josh Comeau.
+:::
+
+### Material UI is a unique use case
+
+Material UI is downloaded millions of times per month and is one of the most rigorously battle-tested UI libraries on the internet, with a GitHub history spanning all the way back to 2014.
+It's had to make some massive changes along the way to keep up with the times; most recently, moving from JSS to Emotion from v4 to v5.
+While those breaking changes did bring many benefits overall, they unfortunately came with a notoriously painful migration experience.
+
+We learned our lesson!
+We can't do that to our users again.
+
+So when it came time to seek out a new way to generate styles, we knew we needed to keep the syntax and authoring experience as similar as possible to Emotion and styled-components, to minimize friction when migrating.
+
+### Other options don't meet our needs
+
+For those of us who are perfectly happy with the patterns we know and love from CSS-in-JS, it feels frustrating to consider abandoning all that muscle memory just to reinvent the wheel yet again.
+We like the DX of colocated styles, and we'd rather not bloat the DOM with atomic class names—so Tailwind CSS, StyleX, Panda CSS, and other solutions that have cropped up in recent months just don't match up with our preferences.
+
+## How Pigment CSS works
+
+Pigment CSS is a zero-runtime CSS-in-JS library: This means it doesn't have access to the end user's browser runtime, which would be necessary to generate and insert authored CSS at run time.
+Instead, it does all its processing at build time to pre-generate the CSS which then becomes part of the output bundle.
+
+Pigment CSS is built on top of the [WyW-in-JS](https://wyw-in-js.dev/) library that also powers [Linaria](https://linaria.dev/).
+It features a [processor](https://wyw-in-js.dev/how-to/custom-tagged-template#creating-a-processor) which makes it possible to create custom logic that's triggered by the presence of different imports from the library.
+The processor looks through the source code for `styled()`, `css()`, and other function calls and extracts the arguments to be evaluated.
+These values are then handed back to Pigment CSS for additional parsing and evaluation.
+
+:::info
+Check out [How Pigment CSS works](https://github.com/mui/pigment-css/blob/master/HOW_PIGMENT_CSS_WORKS.md) for complete details.
+:::
+
+## Benefits of using Pigment CSS
+
+For Material UI users, the benefits of adopting Pigment CSS\* are clear: your end users get better performance, and you get RSC and App Router compatibility without having to significantly change how you author component styles.
+
+_\*These benefits extend to other component libraries beyond Material UI as well, but that's our focus for the sections that follow._
+_We intend for Pigment CSS to be a viable solution for the React ecosystem as a whole, but you can understand why we're prioritizing Material UI during early development._
+
+### Better performance
+
+When comparing the same Material UI app built with Next.js and either Emotion or Pigment CSS, the latter led to:
+
+- 20% reduction in first load JS (104 kB vs. 131 kB)
+- 9% decrease in First Contentful Paint (455 ms vs. 503 ms)
+- 15% reduction in Time To First Byte
+- 7.5% reduction in page HTML (14.7 kB vs. 15.9 kB)
+
+### Familiar developer experience
+
+For developers migrating from Emotion or styled-components, you're probably already familiar with the most common patterns employed by Pigment CSS.
+`styled()` and `css()` are the two main functions used to define styles, and they mostly work the same as you'd expect them to (with some notable differences due to the nature of build-time CSS-in-JS—see [Coming from Emotion or styled-components](https://github.com/mui/pigment-css/tree/master?tab=readme-ov-file#coming-from-emotion-or-styled-components) for details).
+
+We've also ported over the `sx` prop from MUI System, so you can still define styles directly in a given component, but now it's much more performant than before.
+And in Pigment CSS we've extended support for `sx` to include _all_ DOM nodes—not just Material UI components—so you don't need to wrap a simple `<div>` or `<span>` with a Box component to apply theme styles to it.
+
+### Future-proof solution
+
+Though we're still quite early in RSC era, it seems inevitable that the ecosystem as a whole will converge on this new paradigm for React over time.
+Next.js gave us our first glimpse with the App Router; RedwoodJS [recently released their own implementation](https://redwoodjs.com/blog/rsc-now-in-redwoodjs); and many other frameworks and meta-frameworks are currently working out POCs and RFCs to catch up.
+Regardless of how quickly Server Components catch on among developers, it's clear that library maintainers now must support [the two Reacts](https://overreacted.io/the-two-reacts/) (client-side and server-side) to stay relevant into the future.
+
+Pigment CSS, then, is yet another bet from MUI on the longevity and sustainability of the React ecosystem—and a promise that we'll continue to innovate in this space for years to come.
+
+And perhaps most importantly: because Pigment CSS is maintained by the same folks behind Material UI, we'll have a lot more control over how the tool evolves over time to continue to meet our users' needs.
+In a perfect world, this would be the last time you'd ever have to migrate your Material UI app to a new style engine.
+We'll do our best to make that a reality. 🤞
+
+## What's next
+
+Pigment CSS is currently in the early alpha stage of development—the plan is to have a stable version ready to release alongside Material UI v6 later this year.
+When that happens, you'll have the choice to opt in to Pigment CSS incrementally after migrating to v6, giving you all the time you need to migrate on your own terms.
+
+That said, Pigment CSS is available now for experimentation, and we'd love for you to give it a try and let us know what you think—your feedback at this stage could have a major impact on the final product.
+
+## Get started with Pigment CSS
+
+Head to the [Pigment CSS repo](https://github.com/mui/pigment-css/) to learn how to set it up and start tinkering.
+Please feel free to [open a new issue](https://github.com/mui/pigment-css/issues) if you encounter any bugs or frustrations along the way.
+And while you're there, why not ⭐️ star the repo ⭐️ to let us know you're excited and help spread the word to others? 😁