We present a study of a sample of faint radio sources (F$_{1.4GHz}\geq 16\mu$Jy) in the deep VLA field in the SWIRE Lockman Hole. This is an extremely deep 20 cm continuum survey (rms at image center $\approx 2.7\mu$Jy), complemented by observations in X, UV, optical, NIR, IR, and other radio wavelengths.

Thanks to multi--wavelength photometry in up to 11 passbands from $\approx 2300$\AA~ to 4.5$\mu$m, the observed spectral energy distribution of the identified counterparts was used to derive accurate photometric redshifts and to classify the host stellar populations.

A sample of faint radio galaxies in the redshift range $0.3\leq z\leq 1.3$, estimated to be $\approx$90% complete, was then analysed in order to constrain the nature of the radio emission in these sources, and possible evolution with redshift, investigating the contribution of star formation and AGN activity.