What is the name of earths innermost layer

It is simply called the inner core. 

It is a solid ball composed of a iron-nickel alloy with a radius of about 760 miles. 

Earth can be divided into three main layers; the core, the mantle, and the crust.  Each of these layers can be further divided into two parts; the inner and outer core, the upper and lower mantle and the continental and oceanic crust.  Both the inner and outer core is made up of mostly iron and a little bit of nickel.  I hope this helps.

Perimeter? wheres the answers