Shear thinning is a property of certain fluids where their viscosity decreases when subjected to shear stress or force. This means that when you stir or shake these fluids, they become easier to flow. Common examples of shear-thinning fluids include paint, ketchup, and blood. This behavior is important in various applications, as it allows for easier handling and application of these materials. For instance, in the case of paint, shear thinning helps it spread smoothly on surfaces, while in food products, it makes them easier to pour or squeeze out of a container.