��� You're a WW2 survivor in an enemy jail cell held captive forever. You hear the guards talking about an invasion in your country. Here comes the mail man and tells you that you can only recieve one letter and send one letter a day. He gives you paper and a pen. "Write to your family" he sais and leaves. What would you do? Obviousely the guards would read your letter before you send it so you can't tell any one about the invasion. Or can you? Back then it was possible to hide single messages small enough to fit in a period. This has worked and is very useful and easy to track. Now in the year 2000 scientists have taken that to a new level by using human DNA to say actual messages. They have already successfully tried this with this message: "June 6 invasion-Normandy." But this is still a very hard way to send messages and requires an advanced biochemical lab. So remember, look for the DOT!..>:)