The roof tiles have been in the works since Tesla (TSLA) acquired SolarCity in Nov. 2016—and on the market for a year—but until the company filed for a patent last week it was unclear how they worked.

The roof tiles’ claim to fame is that they look like traditional shingles (they come in four styles) while collecting 98% of the solar energy that traditional solar panels do. To perform both of those functions well, the tiles have to look opaque from street level while remaining transparent to the sun. According to the patent, Tesla achieved this by designing a special louvered glass, which functions much the same way a window blind would.

Tesla patent application explains how its solar roof tiles work https://t.co/hHBUrOa8xX pic.twitter.com/jXdXMokTC4

— Yahoo Finance (@YahooFinance) May 8, 2018

Basically, when viewed from the street, the glass reflects light in such a way that the tile looks opaque, or like the broad side of a window blind, whereas from above, sun rays are clear to bake down between the narrow edges of a blind. Except, of course, it’s a lot more complicated than that.

If you want to see it for yourself, head down to your local Home Depot.