The other hobbyists on this thread made some good points about what's being shown in the photos, but I'm a mushroom nerd and wanted to point out a few things just for fun. I've only grown the tasty kind, but since we're looking at cubes I'm going to talk about cubes.

The first item on the mushroom grower's quest is usually spores. This may seem like a large hurtle, but with the exception of three state it's actually not illegal to buy, sell, or ship spores in the US. There's an understanding that the buyer will not be growing anything with them because that would be illegal. A syringe with spores can be found for under $20.

You can see this person's spore germination lab in the second photo.

The bottles with brown liquid are liquid culture media. That's basically a nutritious, sterile broth. A few drops of the liquid from the spore syringe is added to the bottle and the grower lets it incubate until it starts to form mycelium (the main part of the fungus). Behind the jars you can see agar plates. Some people start with the agar and then move to liquid culture. Some use the agar just to isolate strong organisms and remove contaminants. With one big exception, there's no one correct way to do this.

The exception explains the equipment in the back of the photo: sterile work environments and growth media. The bench is a laminar flow hood that pushes sterile air forward across the work bench. The big pots are (I'm making an educated guess here) steam sterilization chambers. The bags contain sterile substrate. Usually grain like oats, rye, or millet. Even brown rice. The grain is cooked in water, drained, then bagged up (as in this case) or placed into modified jars. The containers and contents are sterilized prior to adding the mycelia.

There are a couple of ways to do this, but lets say they're adding if from the liquid culture. Working under sterile conditions, they fill a sterile syringe with liquid, then proceed to inject a few millilitres into every bag. The injection holes are sealed with tape and they're ready to incubate for a few weeks while the mycelia consumes the grain.

Remember: fungi are not plants. They don't grow in dirt. They consume organic matter and eventually form fruit in order to reproduce.

After a month or two the bags should be filled with pure white mycelial growth. It's now mushroom time. They need a drop in temperature and the introduction of fresh air . I would imagine that this grower moves them to that second room and simply opens the bags to admit fresh air. (I use a slightly different method with my tasty mushers, and it's my understanding that this would also work with cubes. I transfer the grain to tubs filled with a damp substrate, wait for it to colonize completely, then adjust the environmental conditions).

In a couple of weeks the fruits (mushrooms!) start to form. After harvest, you can usually rehydrate the block, wait a week, and get a second crop. And also - now that you have mushrooms, you can collect their spores and begin again!

As a hobbyist it was very interesting to see the photos of a small but still commercial scale grow.