How does Lee help Scout see Boo Radley as a human being rather than the monster that she and Jem had always considered him?

I love the simplicity which Lee uses to illustrate this. Boo comes out of the shadows and Scout sees who her guardian angel was. Her simple response is perhaps the most poignant moment in the story. Scout simply says "Hey Boo". It was like they knew each other for a long time and in a sense they did. Scout is gentle with Boo without scaring him. She clasped his hand and didn't say too much else, they were friends. Boo need not hide in his house or lurk in the shadows anymore.