What is the smallest sample size that can be used with RNeasy Mini Kits?

We have purified RNA from as little as 0.5 mg tissue or 100 cells using the RNeasy Mini Kit and verified the quality by northern blot analysis and RT-PCR, respectively. In principle, there is no minimum sample amount for RNeasy technology as all RNA will bind to the spin column. However, due to a very small amount of residual RNA irreversibly bound to the silica membrane, not all RNA may elute at the final step of the isolation. The RNeasy Micro Kit can purify RNA from as little as one cell.