Blisters
A vesicle is small -- it may be as tiny as the top of a pin or up to 5 or 10 millimeters wide.
In many cases, vesicles break easily and release their fluid onto the skin. When this fluid dries, yellow crusts may remain on the skin surface.
Many diseases and conditions can cause vesicles. Some common examples include:
Goldman L, Ausiello D. Cecil Textbook of Medicine. 22nd ed. Philadelphia, Pa: WB Saunders; 2004.
Habif TP. Clinical Dermatology. 4th ed. St. Louis, Mo: Mosby; 2004.