Researchers at the University of Colorado, operating under a grant from DARPA, have demonstrated a new methodology to grow bricks out of bacteria and sand. The technique uses cyanobacteria in a process that doesn’t sound all that different from mixing a yeast starter with flour to make bread. Scientists created a mix of sand and hydrogel (which is basically a special, goopy plastic that’s 90% water). Then they added the bacteria Synechococcus sp. PCC 7002, which is a particularly fast-growing, well-researched strain of cyanobacteria. Over the course of 24 hours, the bacteria produced rigid calcium (biology’s original hard stuff found in bones and shells), which bound the gel into a solid material. The researchers say all of this can be done in a scaffold the size of a shoe box to produce a self-curing brick.