Based on your tag words I am assuming by IC you mean integrated circuit. An integrated circuit is a series of parallel circuits on a semiconductor chip usually made of silicon. They are used in pretty much every electronic device made today, from computers to toasters.
British scientist Geoffrey Dummer first conceived of the idea of the IC and presented his ideas at a research conference in Washington DC in 1952. He later unsuccessfully tried to build an IC. Texas Instruments engineer Jack Kilby built the first successful IC in 1958 and patented it a year later. His initial idea was to make a series of single circuits on silicon chips and connect them together. The semiconductor nature of the silicon chip eliminated the need for bulky vacuum tubes. Kilby later had the idea to put several circuits on the same chip, thus giving rise to the first integrated circuit. He won the Nobel Prize in Physics in 2000 for his work and died in 2005.
They are a series of parallel circuits. Ok! I assumed that.
But what are the series.
Any example! If you don't mind.