How Did Renaissance Artists Create Such Life-Like Paintings?

Imagine you're drawing a portrait on paper, it's easy to make the eyes look flat. But Renaissance artists made people look like they could blink right out of the canvas! They used tricks like shading (called chiaroscuro) and blending colors so smoothly that edges looked soft, almost like smoke (sfumato). This is why paintings from that time feel so alive, it's like looking at a real person.