  Microresonator frequency combs based on the $\chi^{(3)}$ nonlinearity are
nowadays well understood and making their way into different applications.
Recently, microresonator frequency combs based on the $\chi^{(2)}$ nonlinearity
are receiving increasing attention, as they promise certain benefits, but still
require further study. Here, we demonstrate the generation of a $\chi^{(2)}$
frequency comb, initiated via optical parametric oscillation (OPO) in a lithium
niobate mm-sized microresonator. By pumping at 532 nm with 30 $\mu$W of power,
we observe 1-THz-wide comb spectra around 1064 nm with degenerate and
non-degenerate states. We also show that comb generation requires signal and
idler waves to be degenerate in mode numbers and how the fulfillment of this
condition can be identified from the temperature tuning curves. The results
demonstrate the potential to directly generate frequency combs via OPO beyond 3
$\mu$m wavelengths in the mid-IR by puming in the near-IR region.
