There are three ages: Stone Age, Bronze Age and Iron Age. These ages are divided chronologically according to the material with which tools were created: We have the Stone Age in first place since stone was used to make implements. This age is a pre historic period between 8700 and 2000 BCE. In the second place we have the Bronze Age, in which bronze was mainly used to create tools. During this age, early characteristics of urban civilization were found. And finally, we have the Iron Age. During this period, tools and weapons were made of carbon steel (ironworking).
The system of dividing the ages in 3 categories was created by C.J. Thomsen in order to classify objects according to the material with which they were created.