Researchers at Utrecht University have quantitatively mapped the three-dimensional structure of photonic supraparticles for the first time. Supraparticles are microscopic spheres composed of thousands of smaller colloidal particles. Until now, researchers could only examine the outer surface of these structures. Using a combination of super-resolution microscopy and machine learning, the team shows that particles that appear disorganized on the outside are often almost perfectly crystalline on the inside.