Radio astronomers have discovered two molecules never before seen in space in an interstellar cloud near the centre of the Milky Way. So far, about 130 different molecules have been found in space, but they usually contain only a few atoms each. These newly discovered molecules, propanal and propenal, have 8 and 10 atoms respectively. By finding complex molecules like this in space, scientists can get a better idea of the starting materials that Earth had to work with when it formed billions of years ago, and how life could have evolved.