We already know about the dilution process and how the smallest, miniscule amount of something somehow makes it more potent in homeopathic medicine, but we haven't really gone into the ingredients. What kind of stuff is being diluted down to the atomic scale to help cure warts, cancer, and malaria? Pretty much anything you can think of, actually.
The common daisy is used to treat cuts and wounds, while the wild cucumber can handle diarrhea. Witch-hazel will handle hemorrhoids and varicose veins, while duck heart and liver tackles the flu. But don't freak out if you can't find any of these. Stroll into your back yard and find some poison ivy, if you're suffering from joint pain — while you are there, see if you can find a Bushmaster snake, whose venom can supposedly treat a variety of complications and chronic problems. (Don't actually do this, for in reality they will simply bite you until you are dead.)
There are hundreds of ingredients with thousands of uses, like mercury for chronic ailments and even crude oil for your eczema or psoriasis. While many of these substances are inert on their own, some can be problematic if taken in high doses (or, in the case of mercury, low doses). Fortunately, for the folks who use them in homeopathic medicine, the dosages are so diluted, they're essentially absent, and incredibly large quantities would need to be ingested to cause any significant harm.