Skin does get thin as you get older. If you zoom in on skin, you'll see that the two main things that make up skin are collagen and elastin. They get less and less frequent in the skin as you get older. In other words, as you get older, you lose some of the elasticity and you lose some of the matrix that makes up the skin, making your skin thinner and more papery. You can also make your skin thin by using certain drugs, such as steroid creams. This can make your skin very thin and brittle.

The eyes are connected to the visual apparatus in the brain, and collect information for the brain to process. If your eyes were going to do all the filtering and processing of information, you'd have to have the brain inside the eye. Since that's not the way that we've evolved, the eye just takes in the information and the brain does the processing. As for humans only using 5% of the brain, I think any neuroscientist would say that this isn't true. Brains are very expensive to maintain and use a large proportion of the body's energy. Evolution is also known as being very frugal, so if we didn't need to have all the parts of the brain, then we wouldn't have them. Although different parts of the brain are active at different times, if you took away any part of it, you'd end up with a profound disability. If you stimulate a person's brain, you will become conscious of whatever process that part of the brain controls. You can do this by using trans-cranial electromagnetic stimulation (TCMS). To do this you take a big magnet shaped like the number eight and hold it over someone's skull. You can make the bit of the brain it's held over become active. You can make people move their arms and say things when they don't want to.

The way you make sounds with your voice box is that you have these things called vocal chords. These are just flaps of tissue found in your neck just about where that bulge is. That's your voice box. When air rushes out of your lungs past your vocal chords, it makes them vibrate. When they vibrate, a bit like a string on a guitar, they make little vibrations of sound waves, and that's how you talk. When you get a really heavy cold, which is usually caused by a virus, it attacks the cells in your nose and on the back of your throat. This can make a lot of mucus, and the mucus can get onto your vocal chords. When a string has something sticky on it, it doesn't vibrate as well as when you've got a clear string. So when you try and vibrate your vocal chords and they're covered in gloop, they don't vibrate in the way they would normally and make a funny noise. That's why it goes all funny and croaky when you get a cold.