How do citrus fruits create such a strong smell? —

Citrus fruits contain small pockets of liquid which burst upon contact releasing a jet of strong smelling oil into the air. The strong smell is designed to attract animals to the site to help to spread the seeds of the fruit as far as possible. Andrew Dickerson at the University of Central Florida has recorded the squirting motion using high speed cameras to try to understand the exact process of these 'micro-jets' of citrus oil.

https://www.youtube.com/watch?v=e0kLetIr7Zs