Imagine a material cracking — now imagine what happens if there are small inclusions in the material. Do they create an obstacle course for the crack to navigate, slowing it down? Or do they act as weak points, helping the crack spread faster?Historically, most engineers believed the former, using heterogeneities, or differences, in materials to make materials stronger and more resilient. However, research from Georgia Tech is showing that, in some cases, heterogeneities make materials weaker and can even accelerate cracks.