It is a familiar problem: open up the biscuit packet with anticipation, only to find the contents cracked and broken.
By Christine McGourty
BBC science correspondent
Now a student from Loughborough University in the UK claims to have discovered the answer.
Heading for a dunking disaster
Apparently it is not simply because they have been roughly handled or dropped in the supermarket.
It is actually down to interactions between moisture in the air and moisture in the biscuit which take place while the food is cooling down after being taken out of the oven.
Qasim Saleem, the PhD student who carried out the work, baked and studied more than 100 biscuits in the laboratory using a sophisticated laser technique, called digital speckle pattern interferometry.
His supervisor, Dr Ricky Wildman, said the findings could have an important impact on the biscuit business.
He told BBC News Online: "This is very valuable research. It's a £1.5bn industry and just a small increase in efficiency will have a big impact.
Bringing science to bear on the problem
"It could reduce the number of biscuits that need to be thrown away."
The research showed that, during cooling, a biscuit picks up moisture around the rim which causes it to expand.
But at the same time, it loses moisture at the centre, which causes it to contract. This results in the build-up of forces which are ultimately released in the formation of cracks or in the break-up of the biscuit.
Mr Sallem said: "We now have a greater understanding of why biscuits develop cracks shortly after being baked."
He believes the findings will help manufacturers adjust the humidity or temperature of their factory production lines to help them produce "the perfect biscuit" in future.
Dr Wildman said one solution would be to lower the variation of moisture content within the biscuit by cooking them for longer at a lower temperature.
The information could save industry a fortune
That would mean they only absorbed moisture while cooling and expanded smoothly, making them less prone to cracking.
He said the findings applied to a wide range of what are known as "semi-sweet" biscuits, particularly low-fat biscuits.
Unfortunately those used in the research were not fit for eating afterwards, "on hygiene grounds", he added.
The findings appear in this month's issue of the Institute of Physics journal Measurement Science And Technology.