This chapter first reviews the linear first-order non-homogeneous ordinary differential equation. Introduction to statistics and stochastic processes follows. Afterward, it explains the stochastic fluid continuum concept, associated control volume, and spatial- and ensemble-representative control volume concepts. It then uses the well-known solute concentration definition as an example to elucidate the volume- and spatial-, ensemble-average, and ergodicity concepts. This chapter is to provide basic mathematics and statistics knowledge necessary to comprehend the themes of this book. Besides, this chapter’s home works demonstrate the power of the widely available Microsoft Excel for scientific investigations.