MUI!

Bulma is a CSS framework based on Flexbox and built with Sass

A lightweight and modular front-end frameworkfor developing fast and powerful web interfaces.ui framework full HTML / CSS, javascript component , form, theme , dropdown , responsive ...More full than bootstrap or foundation

Skeleton is a small collection of CSS & JS files that can help you rapidly develop sites that look beautiful at any size, be it a 17" laptop screen or an iPhone. Skeleton is built on three core principles:

Materialize is a modern responsive CSS framework based on Material Design by Google

A rock-solid default for HTML5 awesome. HTML5 Boilerplate is the professional badass's base HTML/CSS/JS template for a fast, robust and future-proof site.

Based on Flexbox (CSS Flexible Box Layout Module), Gridlex is a very simple css grid system to quickly create modern layouts and submodules. How it works? The concept is simple: you need to wrap your .col in a .grid. That's all.

Spectre.css is a lightweight, responsive and modern CSS framework for faster and extensible development.

Advantages

A grid system based on the flex display property.

A Vue.js 2.0 UI Toolkit for Web.https://github.com/ElemeFE/element

MWF works together as a series of page types, modules, and components. It’s a system that allows site authors to consider how best to tell the story of Microsoft products and services with confidence that the modular pieces will support and work together.

This project's goal is to be able to create a fully accessible material design styled website using React Components and Sass. With the separation of styles in Sass instead of inline styles, it should hopefully be easy to create custom components with the existing styles.