The mycelium is a mass of tangled threads that form the vegetative part of a fungus. It’s similar to a plant’s roots in how it grows beneath the mushroom's surface.

Here are a few facts about it: 

1. The mycelium can grow and develop for years, competing in a hostile environment of bacteria, viruses, and other fungi ready to consume it. It creates and produces compounds that directly harm its predators to protect itself. One example of a common predator of mushrooms is larvae. Suppose a larva injures the mycelium. In that case, specific compounds are secreted by the fungus that would inhibit pupation, essentially preventing the larva from growing into its second phase and rendering it a larva forever. When larvae are unable to reach their final stage, they’re unable to reproduce and lay eggs that would harm fungi. 

2. The mycelia have thin cell walls that enable enzymes to go in and out and absorb nutrients. This makes the mycelia easier for human consumption. 

 3. Some mycelia contain beneficial nutrient compounds not found in their fruiting bodies. This is because most of a mushroom’s immune and digestive processes occur in the mycelium. Of note, mushrooms fight harmful microorganisms by secreting chemicals that have antimicrobial properties, explaining why mushrooms have these properties innately. [1] 

 4. The mycelial biomass is composed of the mycelium and its supporting substrate that contains extracellular compounds. These compounds are your enzymes, polysaccharides, and protective secondary metabolites that may provide therapeutic benefits.