Chapter deals with the estimation of the figure-of-merit of various organic molecules, which are useful for all-optical switching applications. The question “how to estimate the nonlinear absorption and refractive index of the organic molecules” is also addressed in this chapter. The chapter starts with the investigations of the third-order nonlinear refractive cross section of the CS2 molecules. Various nonlinear organic molecules are explored to select the best materials in terms of the high figure-of-merit values. The question “how to engineer and design the organic molecules to produce high figure-of-merit values for the all-optical switching applications” is addressed in this chapter. In the present chapter, we explore the possibility of obtaining high FOM values in the cyanine-like organic molecules by the selection of various wavelengths. We also discuss the scientific reports about the thiopyrylium polymethine (YZ-V-69) dye dissolved in the carbon tetrachloride, which can show extremely high FOM values near the absorption edge. Moreover, we extend the practical applications by proposing the incorporation of the high FOM material in a slot waveguide geometry to obtain high switching speed.