Shear-thinning fluids, also known as pseudoplastic fluids, are substances that become less viscous when subjected to shear stress or agitation. This means that when you stir or shake them, they flow more easily. Common examples include paint, ketchup, and blood, which all exhibit this behavior. The phenomenon occurs because the internal structure of these fluids changes under stress. In shear-thinning fluids, the particles or molecules align in a way that reduces resistance to flow. This property is useful in various applications, such as in food processing and cosmetics, where easy application and smooth texture are desired.