Sharingan follows three stages of development patterns: One Tomoe, Two Tomoe, and Three Tomoe Sharingan.
After this, the subsequent development of Sharingan due to the loss of their loved ones, which is very rare to witness, is the Mangekyou Sharingan.
Shinobi who have activated these eyes are compelling. Eye wielded at this Stage have different abilities and eye patterns gained based upon their potential, grief and Chakra reserve. The strongest Mangekyou Sharingan we ever witnessed on the show is Shisui Uchiha. His ability was the absolute Genjutsu known as Koto Amatsukami.
In the anime, we see Sasuke activate the two tomoe skipping the first Stage. It means that one can forget the stages if their grief is more tremendous.