How is positioning of Tooltip determined in material-ui?

Question

React

I want to make my own simple tooltip, without using third-party resources, such as material-ui.
I saw some people doing tooltip positioning using findDOMNode. But I don't think this is a very good solution.
Help me figure out how the positioning of the tooltip is determined in material-ui.
I noticed that the tooltip appears at the very bottom of the code, but is displayed near the trigger. How it works?

I'm attaching links:
Tooltip demos
Tooltip CORE
UPD:
I don't mean positioning "top", "left", "right" and so on... But how does the tooltip find the trigger in the tree house and display next to it.