Some interface designs may call for elements to be layered or stacked on top of each other.   There are many ways that elements will naturally stack on top of each other. But we can control this stacking order using a combination of the `position` and `z-index` properties.   In this final episode of AtoZ CSS season one we'll learn about:   The default stacking order of the document What a stacking context is and how they interact with each other How z-index controls layer order within stacking contexts And a method I use for standardising z-index across a project