Kritias Boy (ca. 480 BC)
In the Severe style, sculptors began to make statues more true to life, and with more feeling in their faces and their movements. Instead of all being standing straight up and looking sacred and peaceful, now statues began to do things: drive a chariot, carry something, throw a spear, or ride a horse. They have emotional expressions. (The same thing happened a little earlier in vase-painting). Instead of all being young men and women, Severe Style sculptors carved older people and children too.
This video of the Zeus-Poseidon statue lets you see it from all sides
See how with this statue of Zeus (or maybe it's Poseidon) the statue balances on just one foot and the toes of the other foot? Sculptors had gotten a lot better at balancing their statues. Also, the Zeus statue is in bronze, which is harder to work but much lighter and more flexible than stone.