The correct answer to this open question is the following.
Although you did not specify what artwork you are referring to, we can comment on the following.
Rafael was one of the most important artists during the Renaissance times in Italy. Experts say he was a fantastic painter because he could create the illusion of three-dimensional space, particularly in a painting titled "La Donna Velata." If you see the painting, it is unbelievable the way Rafael used his technique of shading through variations in value. When Rafael uses many colors to create shadows in the painting that make appeared the painting looks in three-dimensions.
That is why Rafael is considered to be one of the greatest painters in human history.