Domino is a small rectangular wood or plastic block, thumb-sized on one end and larger on the other, with either blank or patterned faces bearing from one to six dots or “pips,” resembling those on dice. A set of dominoes consists of 28 such pieces. The term is also used to refer to the games played with them, which fall into two broad categories: blocking and layout games.

The first domino to be struck causes the others to tumble, creating a chain reaction that continues until all are knocked over. This sequence is usually a demonstration of the laws of gravity, and it serves as a metaphor for the way that one event can affect subsequent events. This idea is especially popular in the social sciences, where it has been used to explain everything from the spread of influenza to political revolutions.

Lily Hevesh first learned to play domino as a child with the classic 28-piece set her grandparents gave her. She soon began collecting more and more, and experimenting with different ways to arrange them in straight or curved lines. As her skill developed, she started posting videos of her creations online. Her YouTube channel, Hevesh5, now has more than 2 million subscribers. She has even made domino art for movies, TV shows, and events—including an album launch for pop star Katy Perry.

Hevesh has a knack for combining math, art, and engineering to create mind-blowing domino setups. She plans out each design before she begins, and then calculates how many dominoes she’ll need to achieve her goal. She pays particular attention to the spacing between each piece of the chain to ensure that it will fall in the right order without tripping or falling over.

Physicist Stephen Morris, who has studied the behavior of dominoes, says that each time a player picks up a domino and sets it upright against gravity, it stores potential energy. When the domino falls, much of this energy converts to kinetic energy, providing the push needed to trigger the next domino to fall. Energy then travels from the fallen domino to the ones on its side, and so on, until the entire chain collapses.

The most common domino sets sold in the United States are double-six and double-nine, with 28 tiles in each set. Larger sets are available, but they are not widely used; instead, most players opt for “extended” dominoes, which have a greater number of pips on each end.

The most basic western games of domino are blocking games, in which the pieces are arranged in rows or angular patterns. The players draw for the lead, and then each takes turns playing a domino to the table. The last player to play a domino wins the game.