Abstract
As analytical chemists, the highest resolution measurement one can make is at the single molecule level; it just does not get any better than that. To determine the concentration of a molecule in solution, the best way is to count the number of molecules in a given volume. As long as the volume contains a statistically large enough number of molecules and is above the Poisson noise limit, molecular counting is the most accurate way to make a measurement. Molecular counting is the method of the future and is beginning to be performed today.