I will present first results from a study of a sample of faint radio sources (F_1.4GHz>0.016mJy) in the deep VLA field in the SWIRE Lockman Hole. This is an extremely deep 20cm continuum survey (rms at image center ~2.7microJy), complemented by observations in X, UV, optical, NIR, IR, and other radio wavelengths. Thanks to multi--wavelength photometry in up to 11 passbands from 2300 Angstrom to 4.5 micron, 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 0.3~90% 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.