Effects of Radicals - Free Radicals

Medical interest in free radicals is very recent, but chemists have known all about them and have been studying them closely for about 50 years. When they were first proposed about 100 years ago, most chemists were outraged and protested that they were impossible. Gradually, however, they came to realize that free radicals were very real and were fleetingly involved in many important chemical reactions, such as the formation of plastics (polymers), the perishing of rubber and the deterioration of stored foodstuffs. Most free radicals exist only for very short periods before attacking other substances and being neutralized in the process. They can, however, be produced as quickly as they disappear and when they do attack they can turn other substances into free radicals and so set up very damaging chain reactions.

So, what are they/ to answer that question we must go back to a few very basic scientific facts.