As mentioned, chemistry led to the first detergents, which gave early man his best chance of fighting off microbial infections. It also led to metallurgy and the invention of all sorts of things made from metals. In addition, this branch of science has been responsible for creating artificial fertilisers which have pushed up land productivity greatly, helping the human population to grow. In more recent years, the invention of plastics has been down to chemistry. These materials are now causing an ecological problem and the solution, according to many, may lie once more in the research work of chemists.