" Or think about an elementary-school teacher. She knows her goal: to teach the material mandated by the state curriculum committee. She knows her audience: third graders with a range of knowledge and skills. She knows how to speak effectively—she’s a virtuoso of posture and diction and eye contact. So the goal is clear, the audience is clear, and the format is clear. But the design of the message itself is far from clear. The biology students need to understand mitosis—okay, now what? There are an infinite number of ways to teach mitosis. Which way will stick? And how do you know in advance? "

― Chip Heath , Made to Stick: Why Some Ideas Survive and Others Die