Why do things smell?

Smell is caused by the detection of volatilised chemical compounds (evaporated molecules) in the atmosphere, either organic or non-organic, by neurons located in the olfactory epithelium, a small patch of tissue located at the back of human nasal cavities. The olfactory epithelium’s receptor neurons act as sensory signalling cells, initialising electric signals when odour is detected. When a threshold of stimulus is reached, the signals send that information to the olfactory bulb and cortex – part of the human limbic system (a set of brain structures that form the inner border of the brain cortex) – for processing. The odour is then deciphered, storing and matching the information of the volatilised chemical compounds with other known odours and past experiences.

Video: Giant shock wave

Watch this awesome video of a giant shock wave caused by a massive explosion – and then find out how it all works in How It Works issue 23, on sale 14 July

Science