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Does your dog love to see you after a long day at school? Well, they may be crying happy tears, according to scientists in Japan.

The discovery was made by researchers at Azabu University measuring the amount of tears there were in dogs' eyes during different situations.

They found that dogs really do cry 'happy tears' when reunited with their owners!

The team of scientists found that the dogs they tested had more tears in their eyes than normal when reunited with their owners, but that the amount of tears didn't change when they met someone they didn't know.

Because dogs have lived with humans for so long, scientists reckon the animals may have learned to interact with people to help us understand their feelings.

"Through this process, their tears might play a role in eliciting protective behaviour or nurturing behaviour from their owners," the report in Current Biology journal states.

Lead author of the report, Professor Takefumi Kikusui, was inspired to carry out the research when his poodle had puppies and he noticed the dog had tears in her eyes after giving birth.

"We had never heard of the discovery that animals shed tears in joyful situations, such as reuniting with their owners, and we were all excited that this would be a world first," Kikusui said.

"Dogs have become a partner of humans, and we can form bonds. In this process, it is possible that the dogs that show teary eyes during interaction with the owner would be cared for by the owner more."

This is not the first time that scientists have proven dogs are trying to communicate with humans.

Scientists previously found that the types of dog which we keep as pets have different muscles to animals such as wolves in the wild.

Our pets actually have muscles in their face which allows them to raise their eyebrows and make their eyes appear bigger! So the classic puppy dog eye look that melts our heart is something that dogs evolved to be able to do.