What invention replaced vacuum tubes and made computers faster and smaller?      

Initially, the computer used to be a huge room full of machines. It contained many complex machines that enabled the computer to perform its functions. However, as more and more things were invented, the ultimate size of the computer grew less. The vacuum tube was one part of the computer that allowed the computer to function.

As the computer advanced, transistors were invented. They were smaller and allowed the computers to become smaller than ever. Slowly, the size of the computers decreased as more and more pieces were invented. Today, we have cell phones. Fitting computers on to the hand.