Complex sentence: On the outside, it appears to produce nothing more than fertilizer, but the underground labs of the building hold secret (and possibly illegal) research into genetically modifying living organisms using meteor rocks (Kryptonite).
Split into simpler sentences: On the outside it appears to produce nothing more than fertilizer. But the underground labs of the building hold secret (and possibly illegal) research into genetically modifying living organisms using'meteor rocks' (kryptonite).