Galaxy size evolution tracks. In blue and red, the observed redshift dependence of size distribution of galaxies in the stellar mass range 10.5 < log(M_⋆/M_⊙) < 11, separating between star-forming galaxies (our proxy for late-type galaxies) and quiescent (early-type) galaxies, respectively. The fiducial, theoretical disk size evolution (dashed line) agrees well with the observed evolution of star-forming galaxies. To illustrate the feasibility of spirals to significantly alter the size evolution of individual galaxies, and transition from the population of late-type to early-type galaxies, we show three examples of size evolutionary tracks due to angular momentum transport by spirals, with a variety of spiral arm contrast A, multiplicity m = 2 − 4, and pitch angle i_p, as labeled. The structural transition (in size) is easily accomplished within a Hubble time.