In the geometric growth rate the initial phase of growth is slow and is known as lag phase. This phase is followed by a phase known as exponential phase or log phase. In this phase the rate of growth increases quickly. It is because all the progeny formed after mitotic division undergoes division again and again until the nutrient becomes a limiting factor. Due to the pure nutrient supply the growth rate after the log phase slows down and cease. This phase is known as the stationary phase. When these growth parameters are plotted in a graph against time we obtain a clear ‘sigmoid curve’ also known as s curve.