A population will grow exponentially if it has unlimited resources. To illustrate how rapidly such a population increases, we will examine growth in the common gut bacterium, E. coli. In this example, we establish 5 small colonies of equal size in a petri dish containing a nutrient medium. In these conditions of ample resources, cells divide every 12 minutes, on average. This means that every 12 minutes, the 5 colonies double in area. Once the bacteria become visible, notice how quickly they cover the petri dish. You should get a sense of acceleration, which is what exponential growth is all about.