Here are parts of dried leaves of a stinging nettle plant. In the center piece you can see the hollow stinging hairs which can inject inflammatory phytochemicals into skin. On the bottom left is a 0.5 mm diameter pencil lead for scale. Stinging nettle is used as medicine to treat kidney and urinary problems, rheumatism and gout, among others. There is even a stinging nettle eating contest.
Equipment used: Canon EOS Rebel T5i with 49 mm long extension tube.