All sorts of creatures are living your garden that are never seen mice and frogs and maybe even rats. But did you know that there could be up to 4 million different types of bacteria living in the soil, most not known to science? Researchers now think that there are more bacteria in a tonne of soil - the amount in the average garden - than in the whole of the world's oceans. Compared with the sea, soil offers a greater number of niches for bacteria to live in - for example, with and without oxygen - allowing many different types of bacteria to thrive. So instead of heading off to tropical rainforests to find new creatures, scientists would be better off digging up the back lawn. But they'll need some seriously sophisticated equipment, because these bacteria can only be detected using the same techniques used at crime scenes - DNA analysis.