And we'll talk about what the actual relationship between Viscosity and the resistance is in just a moment. Now, factor number two that affects resistance is the length of our blood vessel. And factor number three is the radius or diameter of that particular blood vessel. Now, by far, the most important physiological factor that influences the resistance inside our blood vessel is the blood vessel diameter. And that's because the blood vessel length. And our viscosity of that blood under normal conditions does not actually change considerably.