The cerebral cortex is a structure that is important to memory, thought, language, consciousness and attention and it's commonly called the "gray matter," for its distinctive color. Most of it's surface is folded in large grooves called sulci. The most recently-evolved part of this area of the brain is called the neo-cortex, which is divided in two hemispheres and takes up nearly three-quarters of the brain’s mass. The thoughts that make us uniquely human—such as personality and logic—occur here.