Biofilms are aggregations of microorganisms that grow on surfaces usually found in environments that have a continuous supply of moisture. They can be made from a variety of microorganisms that include bacteria, fungi, yeasts, and algae. The surfaces they grow on are found in a large array of conditions, like in hot springs and the depths of the ocean. As long as the environment contains the appropriate amount of moisture and nutrients, then the surface they choose could be natural or man-made. Bacterial biofilms first form when bacteria in the moist environment comes in close contact with a surface. Their attachment to the surface depends on two main forces, van der Waals and electrostatic. The first force brings the bacteria closer to the surface, and the negative charge of the bacteria and the surface increases the chances that the receptors will adhere. After the bacterial cells adhere, they multiply and eventually form an extracellular polymeric substance matrix. This structure is necessary to protect the bacterial colonies, and helps them grow through forming nutrient channels. Another feature of this matrix is that it facilitates the co-aggregation with other microorganisms. This allows the biofilm to become more diverse, and usually more pathogenic