> One of the nice things about grid is that you can size the tracks on the parent element
Yep, it's nice to have an alternative to flex (where children determine their own size with flex-grow / flex-shrink / flex-basis).
> Setting height: 100% was also preventing the grid from expanding. Try this JSFiddle https://jsfiddle.net/c3m2194b/
This is an issue I've run into a lot. Well the opposite, when I want overflowing grid cells to gain a scroll bar instead of expanding the parent. Turns out this is only doable if the grid element has an explicitly defined height, which means hard-coding a height like `height: 50vh` or ensuring every ancestor of the grid has `height: 100%` defined, which is pretty gross.
https://jsfiddle.net/36k1079x/