The arrangement and shapes of the patches was chosen so that the front and back of the hand would be distinct but also so that collisions of similar-colored patches would be rare.

With their colorful bacterial colonies in hand, the researchers then created a code using pairs of different colored bacteria.

And I knew they had each made something for me： bookmarks carefully cut， colored， and sometimes pasted together; cards and special drawings; liquid embroidery doilies， hand-fringed， of course.