In general, why are men taller than women?

Height is determined by genetic and environmental factors. And some of the genes determining height, like the aromatase gene, are located on the Y chromosome, which is available only in the males. Therefore, the increased height. 

What is bone made of?

A typical bone has an outer layer of hard or compact bone, which is very strong, dense and tough. Inside this is a layer of spongy bone, which is like honeycomb, lighter and slightly flexible. In the middle of some bones is jelly-like bone marrow, where new cells are constantly being produced for the blood. Calcium is an important mineral that bone cells need to stay strong. 

How do pain killers work?

Your body is full of nerve endings in your skin and tissues. Some of these nerve endings can sense pain, like from a burn or a blow to a body part. When cells in your body are injured or damaged, they release a chemical called prostaglandin.

When you take a pain killer medicine, it keeps injured or damaged cells from making and releasing prostaglandin. When the cells don't release this chemical, it means that the brain won't get the pain message as quickly or clearly. So your pain goes away or becomes less severe for as long as the cells aren't releasing the chemical. The pain killers you take will either disrupt the signal heading from the injured area to the brain, or it will change the way your brain interprets that signal. 

What makes popcorn pop?

A popcorn kernel is actually a seed. At its center is a tiny plant embryo, a life form in its earliest phase. The embryo is surrounded by soft, starchy material that contains water. Surrounding the embryo is a hard shell. When the kernel is heated to about 400 degrees Fahrenheit, the water turns to steam. The pressure from the steam causes the kernel’s shell to explode and the starch to spill out.