Scientist observed natural phenomena and found the existence of ions more than 100 years ago. When the historical background of electrospray was surveyed from the view point of the ionization technique, the origin started by the awareness of the charged drops in nature. Our earth is positively charged and abounds in the positive ion. Iribarne noticed that ions were produced by bubbles at the surface of sea water forming the electric double layer and utilized these fact to create ions. Dole ionized polymers by the hydrostatic electrification of droplets from the hypodermic needle with the Faraday cage as a function of the repeller voltage and originated the electrospray ionization. Cluster ions were separated by the skimmer technique and the positive and the negative ion peaks were obtained. The multiply charged macroion from electrospray ionization was determined. Now electrospray ionization of liquids with quadrupole mass analysis to analyze proteins and nucleotides is one of the main streams of the structural characterization.