What is the main conflict in Solaris by Stanislaw Lem?

Solaris is set in a future time of interplanetary travel. Kris Kelvin is a Solarist, a scientist who studies the planet Solaris, and his specialty is psychology. Kelvin travels to Solaris only to find that the planet's mysterious ocean has begun bringing to life precise duplicates of figures from the deepest recesses of the scientists' minds.