 The cell world is a complex place. Interacting through chemical, electrical and even mechanical cues, our biological building blocks are constantly buzzing with activity. Unfortunately, some of the most popular methods for understanding this bustling world in the lab capture only a slice of the action. While tremendously useful for capturing much of the biology that occurs at the cellular level, the practice of growing and observing cells on dishes and slides misses out on an entire dimension of complexity, meaning that when it comes to predicting how cells actually behave inside the human body, the results of 2D cell biology fall, well, flat. The Fall 2017 special issue of MRS Communications shines a spotlight on how material scientists and engineers are expanding cell research into the all-important third dimension. Just what does a 3D approach to cell biology offer? Perhaps most importantly, it enables researchers to recreate the cellular environment more fully than ever. That might sound obvious, but it's not simply a matter of filling more space with biological material. It's about engineering that space with the right materials. And that's crucial, because over the past few decades, research has shown that cells are just as sensitive to the structure of their surroundings as they are to its chemical makeup. With that knowledge, materials researchers are leading the way towards sophisticated methods of building cell models from the ground up. For some, that involves engineering biological scaffolds with nanoscale features or incorporating more exotic functionalities, such as magnetism, to control shape. Others are choosing to build with gelatin-like biomaterials known as hydrogels, which match the pliability of real tissue and are proving valuable in studying the progression of cancer. And several researchers are choosing to work without a template material at all, using biochemical and mechanical cues alone to coax cells to clump together to form tiny replicas of target organs. Introducing this whole other dimension, however, means an entirely new set of challenges to address. Among the most pressing is figuring out how to adapt microscopy and other techniques for probing cells from 2D to 3D. After all, once cell models are built, researchers need reliable methods of knowing what's going on inside of them. But as highlighted in this issue of MRS communications, bolstered by advances in material science and engineering, researchers are gaining ground in both understanding and replicating the cell world in 3D.