Many bacteria make tiny pores with diameters more than ten-thousand times smaller than a human hair. They use these pores to attack their victims' cells, including our own. The properties of these noxious proteins have been turned to good in several quite different areas of biotechnology, where they are known as nanopores. First, they have been used for various aspects of sensing in which individual molecules are detected. A prominent aspect of this application has been the development of a portable device to sequence DNA by the spin-out company Oxford Nanopore Technologies. Second, nanopores have been used to build tissues, both synthetic and living, by 3D printing, with anticipated medical applications including the screening of therapeutic agents and the repair of damaged organs. The talk will describe both the history of these developments and recent advances, and how the disparate applications of nanopores are connected by the haphazard advances of science.