What is the name of earth’s innermost layer?

Earth can be divided into three main layers: the core, the mantle and the crust

Your answer would be, Core.

(Could also be called inner core)

Think of it as a watermelon, you have the crust, which is the green part, the mantle which is the whitish green part and the red which is the core.

Hope this helps.

In case you didn't get any of that, the answer is Core