When cats are happy, they may squeeze their eyes shut.
10
Sandy, an African Penguin, has been in 'love' with her keeper at the Nuremburg zoo since 1996.
34
Kissing releases masses of oxytocin, a "love potion" that helps couples bond and feel more attracted to each other.
13
Dolphins have names for one another.
18
In 2011, archaeologists discovered the skeletal remains of a Roman couple who have been holding hands for 1,500 years.
81