Cell migration involves dynamic changes in cell shape. Intricate patterns of cell shape can be analyzed and classified using advanced shape descriptors, including spherical harmonics (SPHARM). Though SPHARM have been used to analyze and classify migrating cells, such classification did not exploit SPHARM spectra in their dynamics. Here, we examine whether additional information from dynamic SPHARM improves classification of cell migration patterns. We combine the static and dynamic SPHARM approach with a support-vector-machine classifier and compare their classification accuracies. We demonstrate that the dynamic SPHARM analysis classifies cell migration patterns more accurately than the static one for both synthetic and experimental data. Furthermore, by comparing the computed accuracies with that of a naive classifier, we can identify the experimental conditions and model parameters that significantly affect cell shape. This capability should-in the future-help to pinpoint factors that play an essential role in cell migration. A cell's migration behavior depends on the state of the cell, extracellular environment, and signals from other cells 1. We can study the mechanisms of cell migration by, e.g., knocking out a certain gene or altering the structure of the extracellular matrix (ECM) and testing whether these changes affect cell migration patterns, such as cell trajectory, shape, or shape dynamics (Fig. 1). To compare migration patterns in an objective and statistically sound way, they have to be automatically analyzed and quantified 2. Whereas both cell trajectories 3,4 and cell shape 5,6 can be quantified with a multitude of available methods, the analysis of shape dynamics-especially in 3D-received considerably less attention. When analyzing cell shape in a static fashion, we look at just one snapshot of the cell's migration history. Depending on how we choose this snapshot, we may either miss important differences in cell shape-e.g., if cells transiently appear similar but have different migration patterns-or detect spurious differences-e.g., if cells occur in different phases of the same migration pattern. Even averaging cell shape descriptors over time 7 may not always be sufficient to distinguish some migration patterns, for example when all cells evolve through similar phases of cell shape but different cells do this with different frequencies (Fig. S1) 8. To distinguish such details of migration behavior we need dynamic shape analysis that takes into account relative changes in cell shape between consecutive time points. While such dynamic shape analysis has been done in 2D 8-11 , 3D shape descriptors have not been applied to characterize and compare the full dynamic migration patterns of cells. The ultimate goal, however, is to understand how cells migrate in living organisms 12. Due to advances in intravital microscopy 13-15 , we have increasingly more 3D + time data of cells migrating in vivo and we should exploit the potential of 3D methods to analyze these data 16. Although there are many simpl...