Biometric identification can be divided into three major categories of characteristics: biological characteristics (DNA blood), morphology, and behavior. Morphology refers to shapes, palms, fingerprints, vein patterns, faces, irises, retinas, voices, ears, etc. Behaviors include walking, handwritten signatures, keyboard strokes, etc. These two types of biometric characteristics can be thought of as morphological and behavioral characteristics.

Each bioassay has its advantages and disadvantages, depending on the extent to which it changes over time, the quality of the capture and the frequency of use. For example, a person's voice may change occasionally or even permanently.