Angular Sizes of $\mu$Jy Radio Sources.

We made two new sensitive (rms noise sigma_n ~ 1 microJy/beam) high resolution (theta = 3.0" and theta = 0.66" FWHM) S--band (2 ~ 5 microJy have angular structure phi = 0.3" +/- 0.1" FWHM and an rms scatter sigma_phi ~ /2.43 ~ 0.12", so the median effective radius of star-forming galaxies at redshifts z~1 is ~ 1.0 kpc.