changing font size of material-ui buttons, and having the buttons scale?

Use the labelStyle prop to override the inline style for the element

http://www.material-ui.com/#/components/raised-button

<RaisedButton
    label="Button" 
    labelStyle={{ fontSize: '63px'}}
/>

The problem is Material-UI inlines all of the styles for their components, so if you try to override them with CSS selectors it doesn't usually work quite right. Instead, try overriding whatever inline styles you don't want using the style property directly on the component. It would look something like this:

<RaisedButton style={{ fontSize: '63px' }} label='Log in Here' />

And if it still doesn't look quite right, just inspect all the generated inline styles on that component and see what you'd like to change, then just add that to the style object as well.

http://www.material-ui.com/#/components/raised-button