This unit is rich in theory and application. Basic exponential functions are reviewed with the method of common bases introduced as their primary algebraic tool. Exponential modeling of increasing and decreasing phenomena are extensively explored in two lessons. Logarithms are introduced as the inverses of exponential functions. Special care is taken to develop good number sense concerning logarithms before standard work is done with logarithm laws. Equation work with logarithms emphasizes both solving equations that involve logarithms as well as solving exponential equations with logarithms. The number e and the natural log are briefly introduced with the unit ending by revisiting regression in its exponential and logarithmic forms.