Well, the first bit is easy to answer. C. elegans is a worm. The second bit ... that's trickier. Let's just say it started with one scientist making a joke that a bunch of others didn't appreciate. Anyway, back to the C. elegans (full name Caenorhabditis elegans). It's a tiny soil-dwelling worm, about 1mm long. It's also transparent, and mostly hermaphroditic. While all of that is interesting, C. elegans is most well known for its role as a model organism.

Model organisms have nothing to do with fashion, but a lot to do with helping us understand different biological phenomena. They're species that are studied intensely, and the information gathered gives us insights into how other organisms operate. In medicine, model organisms help us to understand disease, and allow testing of drugs or other treatments. Very handy when experimentation on humans would be dangerous or unethical. Of course we have to be careful about drawing generalisations from one species to another (keep this in mind when reading that there is a cure for cancer, or Alzheimer's - and the studies are in animals), but model organisms have increased our understanding of everything from neuroscience and behaviour, to reproduction and development.

C. elegans is just one model organism. Others include fruit flies (or Drosophila), widely used in experiments in genetics, and zebrafish (scientifically known as Danio rerio), often used to study early development. Some model organisms are much simpler - like the bacteria E. coli, or the yeast Saccharomyces cerevisiae (commonly known as bakers yeast). Others are more complex, like laboratory rats and mice. In the plant world it's Arabidopsis thaliana (thale cress) that takes the crown as the most used model of plant biology and genetics.

Despite some obvious differences (on the surface a fruit fly and a zebrafish don't have much in common), these model organisms all share a few things that make them useful in scientific research.

They're generally small, have a short life cycle, and can be kept and grown easily in a laboratory. And, importantly, we have techniques for manipulating and analysing them. So thanks Twitter for giving a humble worm its five minutes of fame, and allowing me to introduce you to some of the non-human models of the world.