Dim sum is linked with the older tradition from yum cha (tea tasting), which has its roots in travelers on the ancient Silk Road needing a place to rest. Thus teahouses were established along the roadside. Rural farmers, exhausted after working hard in the fields, would go to teahouses for a relaxing afternoon of tea. At first, it was considered inappropriate to combine tea with food, because people believed it would lead to excessive weight gain. People later discovered that tea can aid in digestion, so teahouse owners began adding various snacks.
For many in southern China, yum cha is treated as a weekend family day. Consistent with this tradition, dim sum restaurants typically only serve dim sum until mid-afternoon (around the time of a traditional Western 3:00 coffee break), and serve other kinds of Cantonese cuisine in the evening. Nowadays, various dim sum items are even sold as take-out for students and office workers on the go.
[embedyt] http://www.youtube.com/watch?v=E2cM9VHGOL4[/embedyt]