That stuff that collects in the earpiece of your phone and, in particularly extreme cases, all over the receiver.

Most commonly found nestling grimily in the nooks, crannies and crevices of office telephones* due to the cursory wave of the duster that passes for thorough cleaning in the workplace .

I have, through years of time-consuming and painstaking research, identified six prime causes for telephone detritus:

5)Sundry food products
6)Dead skin cells

When starting a new job, it is common for people to remove the existing build-up of telephone detritus, so they can start their tenure with a nice clean phone. They can then set about transforming the round indent of the earpiece into a veritable talking Petrie dish, alive with new, personalised organisms, germs and bits of stale croissant, unique to themselves.

*If you have telephone detritus on your home phone you must have a very scummy house indeed, and I do not wish to be invited round for dinner.