Dominoes originated in China in the 12th Century as developments from dice. Each Domino tile was designed to represent one of the 21 combinations of results of throwing two separate dice:
1:1 1:2 1:3 1:4 1:5 1:6
2:2 2:3 2:4 2:5 2:6
3:3 3:4 3:5 3:6
4:4 4:5 4:6
Original Chinese Dominoes sets were made of black tiles with red and white dots and also featured duplicates of 11 of the combinations, hence comprising 32 tiles in total. The tiles were also split into suits called "Chinese" and "barbarian".
Tiles with blanks were known to have existed in China in the 17th Century. It was these kind of dominoes that first came to Europe in the 18th Century initially to Italy and have developed into the 28 tile sets that we know today.
European dominoes didn't feature suits or the duplicate combination tiles, but did subsequently become extended to allow more players to be involved in the games by increasing the number of potential dots on each end of the domino. There are therefore now double 9, double 12 and double 15, double 18 and even double 21 sets available although these are rare as they have 253 pieces which is more than is really needed for most games.