Imagine that you're four or five years old. Do you remember the perspective from which you viewed the world? Everything was bigger than you were, especially the things that frightened you, like locomotives, planes, clowns and elephants. You were little and easily frightened. A needle poke in the arm for a venipuncture blood draw was likely to be a traumatic experience.
One of your worst fears was pain. Some pain you accepted as the price of having fun. Running, jumping, climbing trees and roller skating all involved pain when you fell down. Unless the injury was worse than usual (or your Mom was nearby), you'd just pick yourself up and go back to playing.
Other pains were much worse and more frightening, especially anything involving needles. Getting shots was terrible, but having blood drawn via a needle in your arm was worse.
Drawing blood from a young child can be difficult for everyone: the child, the parents and the laboratory technician. Children have a layer of subcutaneous fat that is protective from both injury and famine. But that fat buries their veins very effectively. Not until puberty do the veins start to be well defined. Before that, finding a vein requires at least a couple of minutes with a tourniquet tied tightly around the arm and some probing with a needle.
The whole experience is not only painful, but terrifying to the child, who has no idea why he or she is being attacked in this way. Sometimes the child has to be restrained in order to obtain the blood, which causes further trauma.
The blood is obtained from a single drop from a fingerstick, withdrawing far less blood from the child and far less painfully. The pain is so brief that most children don't even cry. They watch with fascination as the blood is drawn up into capillary tubes. Microsampling keeps kids calm, parents relaxed, and laboratory technicians sane.