Getting people to donate blood isn't the easiest thing to do, but Publicis Sao Paulo and Fundação Pró-Sangue may have figured out the secret to it.
Mobile phone users constantly have their batteries drained and with this poster, people can plug in their phones to a red-colored cord, which is made to look like the equipment that's drawing blood from the arm on the poster.
There's a small ledge underneath the advertisement too, but since you can't go far without leaving your phone unattended, it's pretty hard not to look at the poster, which provides a gentle, encouraging message that simply says: "If you need, we’re here for you. Why not return the favour? We need blood."