Figure 1. Different classes of COCs (de Wit et al., 2000). Class A. Oocyte is surrounded by a compact cumulus with a homogeneous cytoplasm. Class B. Oocyte is surrounded by a less compact and darker cumulus. The cytoplasm is dark and moderately granular. Class C. Oocyte is surrounded by dispersed cumulus cells. Oocyte has a granular cytoplasm. Reproduced from Lasiene et al. (2009) with permission.