You might not know the name (yet), but you’ve seen them: zellige tiles (also known as Moroccan tiles, zellige terracotta tiles, and zilij) are the trendiest tiles of 2019. We’ve seen them pop up everywhere we’ve looked the past few months, from a villa in France to a trendy house in Hudson to a cottage on Cape Cod. Their appeal? A handmade, slightly imperfect charm.

If you’re thinking about installing the tile of the moment in your house, there are a few things you should know—from how to tell if it’s the real thing to why it’s not ideal for perfectionists. Read on before installing:

1. It’s an ancestor of subway tile.

Zellige and subway tile seem worlds apart: one was created in 1904 for the New York City subway, the other dates to the 10th century in Morocco. But zellige was actually an early iteration of the ever-popular subway tile: both are ceramic tiles which have been fired and glazed. Read more in Remodeling 101: A Guide to the Only 7 Types of Tile You Need to Know.

2. It’s a prized (but dying) art.

The art of making zellige is passed from generation to generation in Morocco; master craftsmen are called maâlems. But even as it’s having a resurgence in interiors, it’s a dying craft, reports USA Today.

It’s laborious work. To make traditional zellige tiles, natural clay (usually from the area of Fez, Morocco) is mixed with water, hand-shaped, dried, and then kiln-fired, often using olive pits. Enamel glazing is then applied to the fronts of the tiles by hand. As with prized goods in other parts of the world (Champagne, Belgian linen), Morocco recently required that true zellige tiles be made from a clay without lime or iron, both of which can damage the tiles, and labeled accordingly.