toxicology

Is there any substance out there in which one molecule of it can be fatal? I think we've all heard the axiom about dosage being everything. This can be proven wrong if there is even just one substance where the indivisible part of it would be fatal. So just looking for any positive evidence...

As I understand it, homeopathy claims to take the 'essence' of a substance in order to imprint some sort of benefit when ingested. Criticism includes the claim that some homeopathic remedies have been distilled of any remaining medication. Some of the homeopathic remedies are considered to be...