docs/data/system/getting-started/overview/overview.md
MUI System is a set of CSS utilities to help you build custom designs more efficiently. It's used internally by libraries like Material UI, Joy UI.
MUI System gives you a set of flexible, generic wrapper components like Box and Container that can be quickly customized using the sx prop.
This prop lets you define styles directly within the components themselves, rather than creating bulky and redundant const definitions with styled-components.
It also gives you direct access to your theme's custom design tokens to ensure consistency in one-off styles.
Learn more on the sx prop page.
sx prop can replace dozens of lines of code.sx prop features a superset of CSS, so it's intuitive to pick up and start working with right away if you're comfortable with CSS.