The word Insomnia means?

• Difficulty falling asleep
• Difficulty staying asleep
• Difficulty returning to sleep after waking
  

The Earth can be divided into four main layers: the solid crust on the outside, the mantle, the outer core and the inner core. Out of them, the crust is the thinnest layer of the Earth, amounting for less than 1% of our planet's volume.

During exposure to sunlight 7-dehydrocholesterol in the skin absorbs UV B radiation and

is converted to previtamin D3 which in turn isomerizes into vitamin D3.

Cholesterol is made mainly in the liver.

But it's also found in animal foods such as eggs, shellfish, meat and dairy products.

Groundwater is water that exists underground in saturated zones beneath the land surface.