A simple method to produce aggregates of dendrimers in a form of nanometer-sized round dots over an area measured in centimeters is presented. The method is based on rapid evaporation of a solvent from a thin cast film of an electrolyte solution of polyamidoamine dendrimers on mice. Chemically specific adsorption, electrostatic interactions, phase transitions, and dewetting instabilities are shown not to be responsible for the dot formation. Changes in temperature and humidity have only little effect. There is a threshold evaporation rate above which the dots are formed. Once formed, the dot size and spacing are independent of the evaporation rate. The dot is also formed by different types of dendrimers and solutes, demonstrating the wide applicability of the present method.