To put a number on it, that means the 10 million or so species identified so far represent a drop on the ocean of as many as one trillion total species. As a point of comparison, consider that current estimates suggest that our home galaxy the Milky Way may contain between 100 and 400 billion stars. This is a big number, with possibly big implications.

The new estimate draws on big data analyses which suggest that biodiversity operates on an exponentially sliding scale. At the level of biological complexity within us big mammals, there's not a huge number of organisms. But by the time you get down to the microbial level – to microorganisms like bacteria – the number balloons.

To complete their study, the scientists took tens of thousands of existing records to assemble a dataset of more than 5.6 million species (both micro and non-microorganisms) from 35,000 locations around the world – spanning all continents and oceans except Antarctica. By analyzing this data, they found that many previous estimates of biodiversity significantly under-sampled microorganisms – the populations of which have been scrutinized more deeply in recent years.