This tutorial is addressed to a general audience willing to familiarize itself with the fundamental factors that control the efficiency of modern chromatographic columns (fully porous particles, core-shell particles, monolithic columns) in liquid chromatography. The experimental methods developed for the determination of the universal reduced HETP plots, h(n), and its three main contributions are presented and explained in details. They will include the peak parking method for the determination of the longitudinal diffusion HETP term, B/n, the selection of the most relevant model of effective diffusion in chromatographic beds for the determination of the solid-liquid mass transfer resistance, Cn,  and the numerical peak integration method for the measurement of the eddy diffusion term, A(n). The results will be discussed for standard fully porous particles, sub-3 mm core-shell particles, and for the monolithic columns of the first and second generation. Eventually, it is shown how the accurate knowledge of the h(n) plots can be used in practice to rapidly assess the expected efficiency and, so, the level of peak resolution of commercial columns operated in a large spectrum of experimental conditions. This covers the analysis of small and large compounds (from MW=100 Da to MW=50 kDa), the application of high temperatures, supercritical mobile phases, and ultra-high pressures in fast liquid chromatography.