After 100 years, automobiles still need engine oil, transmission fluid, brake fluid, antifreeze, power-steering fluid, and so on. Wouldn't it be great if just a single multipurpose fluid could be circulated from a central reservoir? Each part would use only the needed properties of the fluid, exclude detrimental properties, and then send it back.

Most people north of the equator have an observable suntan by August. Ironically, a desire to be outside is often coupled with another strong desire to get out of the sun, as indicated by sales of sun umbrellas and other types of sunshades.

A key design feature shared by many 100-year-old barns and some modern skyscrapers is that the external shell carries the building's load with a minimal use of internal columns for support. Internal floors and walls, if any, function in a structural way to stiffen the building.

The eye is an amazing instrument, but it does not function alone. Even with visual receptors rapidly sending data along the optic nerve, no mental image will form at all unless the brain is properly equipped to manage the input. One data processing feature of the brain enables what is called perceptual stability.

Sea urchins are spiny marine animals. Some of them like to hide in holes that they dig out of limestone in the ocean floor, using teeth that are ground down and yet remain sharp. What makes these teeth so special that they can drill through rock and not go blunt?