1) Elvis Presley, often referred to as the "King of Rock and Roll," has sold over one billion records worldwide.

2) A newborn kangaroo is about 1 inch (2.5 centimeters) long and weighs less than a gram.

3) The first consumer digital video recorder (DVR), the TiVo, was introduced in 1999 and allowed users to record and store television programs for later viewing.

4) The Earth's core is primarily composed of iron and nickel and is as hot as the surface of the sun.