Article about Forensic Science

Spies could hide messages in gene-modified microbes

spies can now send messages hidden in genetically engineered bacteria. The new method, dubbed steganography by printed arrays of microbes (SPAM), uses a collection of Escherichia colistrains modified with fluorescent proteins that glow in a range of seven colours.
Every character of the message is encoded using two colours, creating 49 possible combinations. That is enough for the alphabet, the figures 0 to 9 and a few other symbols too. 
'Messages' are grown on agar plates then transferred to a thin film that can be sent in the post to the recipient. The film appears blank in everyday conditions, but the message is revealed when the recipient transfers the bacteria to an appropriate growth medium.
I find this really cool and interesting as now people can send secret messages without people finding out. They would not know what the message is saying until they put it in a specific place so the bacteria can grow. This would mean that people can now have messages that only the personal who knows how to 'unlock' can read it.