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Galaxy formation entails the hierarchical assembly of mass, along with thecondensation of baryons and the ensuing, self-regulating star formation. Thestars form a collisionless system whose orbit distribution retains dynamicalmemory that can constrain a galaxy's formation history. The ordered-rotationdominated orbits with near maximum circularity $\lambda_z \simeq1$ and therandom-motion dominated orbits with low circularity $\lambda_z \simeq0$ arecalled kinematically cold and kinematically hot, respectively. The fraction ofstars on `cold' orbits, compared to the fraction of stars on `hot' orbits,speaks directly to the quiescence or violence of the galaxies' formationhistories. Here we present such orbit distributions, derived from stellarkinematic maps via orbit-based modelling for a well defined, large sample of300 nearby galaxies. The sample, drawn from the CALIFA survey, includes themain morphological galaxy types and spans the total stellar mass range from$10^{8.7}$ to $10^{11.9}$ solar masses. Our analysis derives theorbit-circularity distribution as a function of galaxy mass,$p(\lambda_z~|~M_\star)$, and its volume-averaged total distribution,$p(\lambda_z)$. We find that across most of the considered mass range andacross morphological types, there are more stars on `warm' orbits defined as$0.25\le \lambda_z \le 0.8$ than on either `cold' or `hot' orbits. Thisorbit-based "Hubble diagram" provides a benchmark for galaxy formationsimulations in a cosmological context.

The stellar orbit distribution in present-day galaxies inferred from the CALIFA survey