The thing about our clan that makes us more infamous is the fact we were called evil. This was due to use using our eyes as ways of getting things done the way we wanted. We didn’t like having others being equal to use, so people went so far is to killing their own friends or loved ones for power. It made us lust more for this superior position in the clan.
The eyes evolved over time due to the love and hate of the clan. We hated others who was ahead of us, and wanted to destroy what we see was irrelevant. We wanted to fill the void that our hearts got when we awakened our sharingan. This was however the faith they all shared and eventually died out from the massacre Itachi did. It was to save the clan from its own curse.
The sharingan first of all is one the great three dojutsu of this world. It comes from the extinct Uchiha clan who was feared for this eye. It’s the clan’s symbol of power and kekkai genkai. The sharingan is unlocked when the user is under a lot of emotional stress, weather it is happy or sad. It varies from user to user.
What makes third stage more advance then second is the general growth of the abilities. Now able to pierce through genjutsu up to B-Rank, the user learns how to cast genjutsu through the eyes. The perception of the user is far better now, able to mimic basic movements down to the very detail it needs.