Abstract An introduction to randomness and the neutral theory of molecular evolution and how it contributes to levels of genetic diversity in populations. The estimation of random shifts in allele frequencies over time is discussed using the binomial probability distribution. This chapter visualizes how different initial allele frequencies relate to their probability of being fixed in a population when only drift is acting. The outputs of multiple simulations of a population undergoing random increase and decrease in allele frequencies per generation are built, run, and visualized. The fixation index (F) is introduced to quantify the loss of genetic variance over time.