To get to know oneself
If a person doesn't know, who and what kind of character it is, then the best way to find that out, is to look at it's past. The past here means person's parents, grandparents and so on. A genealogical study. It's possible to tell, what are the traits of a person just by looking at it's face, or it's palm (fingerprints), or DNA. The face is the easiest thing to see. One just has to know, what does every feature of a face mean. The meaning of each feature can be found out by studying characters of relatives and presense/absense of a specific trait together with a specific feature of a face.