Whats the difference between JSS and Styled-components?

For my next project I am planning to use advance methods to create and use stylesheets. I have read about these two projects – JSS and styled-components.

But I am really confused over what to use. The guys at Material-UI are using JSS which is fun, but I have heard that Styled-Components can be truly cross-platform which will allow me in future to use it for both React-web based apps and React-Native apps.

I need to know how they are good for PWAs and do they support latest W3C specs for CSS?