While browsing around a department store, a man came across a Thermos flask. Not having seen one before, he asked the assistant what it was for.
The assistant explained that it will keep hot things hot and cold things cold.
Impressed, the man bought one – the next day he took it to work to show off to his work-mates.
‘Look at this,’ he said. ‘It’s called a Thermos flask, it keeps hot things hot and cold things cold’.
‘What have you got in there?’ asked one of his colleagues.