You knew the answer, right? I’ve always loved photography, and I’ve read a bit about its history, so I was able to answer this question correctly.
Here’s a bit of information I found:
Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thinner than common window glass.
Glass plates were far superior to film for research-quality imaging because they were stable and less likely to bend or distort, especially in large-format frames for wide-field imaging.
— From Wikipedia
For more interesting reading, check out this NAQT article: You Gotta Know These Photography Pioneers
You may already be familiar with Louis Daguerre, but how about Joseph Nicephore Niepce? I’d never heard that name before. Niepce created a process known as heliography, and he used it to create View from The Window at Le Gras, the oldest surviving photograph of a real-world scene. Shown below is the original glass plate and an enhanced version.
Niepce later partnered with Daguerre to create the physautotype method, which used lavender oil. Following Niepce’s death, Daguerre went on to develop the process which bears his name — daguerreotype — using an iodized silver plate which was exposed to light, treated with mercury fumes, and then “fixed” with a solution of sodium thiosulfate.
Amazing, isn’t it, that today we simply grab a cell phone, point, and click. We owe so much to the pioneers of photography who looked for ways to capture the beauty of the world around them.