https://codesandbox.io/s/codesandboxer-example-forked-4owo3?file=/example.js
Without marginTop: 50 in styles.container, the InputLabel is not shown.
@Ploppz That is how the Material-UI InputLabel component works.
It is designed to be used as a floating label, so it has to be positioned relatively to the container of the input element to support this.
If you don麓t need to use the floating label feature, you could change the style of the component as follows:
<InputLabel style={{ position: 'static', transform: 'none' }}>Label</InputLabel>
As @Rall3n said, InputLabel is positioned 'absolute' to the top let, so this should be expected behavior.

I'll close this issue now as it does not pertain to any defective aspect about react-select, but as a side note, getting MUI TextInput to play nice with react-select is on my long running to-do list.
Thanks!