Since, from a long time we have learned and studied that earth have only four layers inside it .

1. Crust 
2. Mantel
3. Outer Core 
4. Inner Core

But shocking after a long research scientist have finally found a fifth layer lurking beneath the earth. As a result of which all the geography and science textbooks have to re-written as scientists from the Australian National University (ANU) have confirmed that the Earth’s structure is made up of five, not four, layers. As we all have generally seen the digram of our earth in textboks which looks like this 

But after the new discovery this all got changed as the above figure seems to be some missing part that is the latest core of our earth which is also known to be "The Inner-most Inner Core " of the earth.

How scientists found out the fifth layer?   

Sceintists were examinng the behavior and character of sesmic waves on the surface and beneath the earth. Apparently they found a strange partten on the of the waves bouncing from surface to center  and again to the surface which is a strange phenomena which is only possible if the sesmic waves strikes to a hard solid surface. But as we earlier have studied that earth consists of four layers in past and the inner core is made up of moltel metals like mostly Iron(Fe), whose radius is  about 1,220 kilometers (758 miles). Since scientists made a prediction that there must be a solid core to reflect the waves to the surface.

After this incident in 2002 scinetists started to collect the data of differnet eathquakes of of magnitude 6 or higher of 200 earthquakes for more than a decades and came to conclusion that earth do have a fifth core which is hard solid state form of purely Iron(Fe) and Nickel whose radius is about 400 miles(643.738 kilometers). It is formed due to the intense pressur and temprature which some what looks like

Ad this is  a new break through but some scinetist a opposing this this discovery.“There are still many unanswered questions about the Earth’s innermost inner core to be proved as the official fifith layer." Let's see where it goes.