In the world of chemistry, polarity is used to refer to a separation of electric charge. Generally speaking, polar molecules such as sucrose and hydrogen fluoride will dissolve in water, while non-polar molecules such as those found in oils and fats do not. This explains the popular "oil and water" axiom as both molecules demonstrably do not mix.
A study by the United States National Library of Medicine was carried out on a system of eight independent caffeine molecules in a box of water and found extensive aggregation of the caffeine molecules.
The same study found that caffeine molecules are weakly hydrated and easily separate out of water into non-polar fluids. It is this aquaphobic tendency that allows manufacturers to easily create low caffeine or completely caffeine-free beverages.
Caffeine belongs to a family of compounds known as purines. From a health perspective, the term is well-known to people who suffer from gout. Other health related studies have proved inconclusive, with many showing no correlation with caffeine intake and osteoporosis or most types of cancer, while there is continuing controversy over whether or not it may be linked to increasing blood pressure or miscarriage.