I am a planetary scientist specializing in the study of exoplanet atmospheres. Exoplanets are planets that orbit stars other than the Sun. We can observe their atmospheres when they pass in between us and their parent star; light from the star filters through the planet's atmosphere, and different gases in the atmosphere absorb certain wavelengths of light, leaving fingerprints on the light that makes it as far as our telescopes. I use computational models of light passing through atmospheres to compare with the data from telescopes, which helps us to work out which gases are present in each planet, and in what amounts. This tells us a lot about how those planets have formed and evolved, and helps us to compare exoplanets with our better known companions in the Solar System.