Cut various food items into small pieces. Let a friend of yours be blindfolded. Put a nose clip on his nose so that he can't smell the food. Now put a piece of an item into his mouth and see if he can identify it. Let him wash his mouth and repeat the experiment, with a number of items. After that remove the nose clip and repeat the experiment. You will see that there is an improvement in accuracy in identification.
The Blood Vessels in Your Eyes
Go into a room at night and light a candle. Then switch off the electric light. Ask a friend to hold the candle about a foot to the side of your eyes. You will see the shadows of the blood vessels in the retina. The brain is used to see the light coming from the front. So what it does now is try to understand the shadows that fall inside due to the blood vessels.