There are many ways to create three dimensional objects on a micrometer scale. But how can the chemical properties of a material be tuned at micrometer precision? Scientists at the Vienna University of Technology developed a method to attach molecules at exactly the right place. When biological tissue is grown, this method can allow the positioning of chemical signals, telling living cells where to attach. The new technique also holds promise for sensor technology: A tiny three dimensional “lab on a chip” could be created, in which accurately positioned molecules react with substances from the environment.