Steel is not a single product. There are more than 3,500 different grades of steel with many different physical, chemical, and environmental properties.

Approximately 75% of modern steels have been developed in the past 20 years. If the Eiffel Tower were to be rebuilt today, the engineers 

would only need one-third of the steel that was originally used.

Modern cars are built with new steels that are stronger but up to 35% lighter than in the past.