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Although the bodies of many animals are (more or less) symmetrical on the outside, their internal organs are asymmetrical. For example, the heart is on the left, and in order for it to develop in this position the heart cells must ‘know’ which side of the body is going to be the left side and which will be the right. To try and understand how this happens, I study the embryos of zebrafish (a tiny tropical fish that lots of people keep in aquariums). Their embryos are really useful because they develop very fast: in just 24 hours they have a heart that beats and pumps blood around the body. They are transparent too, which means we can see what’s going on inside the body as it is developing! Many things that we learn from studying zebrafish can help us to understand other animals too, even humans.

My day usually starts with a visit to the aquarium, because zebrafish lay their eggs first thing in the morning (at sunrise ie. when we switch the lights on). After collecting the eggs I take them to the lab, have a look at them through the microscope to see that the cells have started to divide, and then I leave them in the incubator to develop. After coffee time, I’ll get on with experiments (most of which involve very small tubes of DNA and other molecules, and will hopefully tell me whether genes are switched on or off). Later in the day, I check my fish embryos again to see how they are developing. By the time they are 12 hours old, they ‘know’ which side of their body is going to be the left and which will be the right, so I do most of my experiments before this time. And then, it’s home time.