Pleurotus ostreatus which is known as the oyster mushroom, the pearl oyster or the grey oyster mushroom is a very common edible mushroom. It was first cultivated in Germany as a survival measure during World War I and is grown commercially around the world. It is related to the likewise cultivated king oyster mushroom. The oyster mushroom is easily recognized by the way it grows on wood in shelf-like clusters, usually in large size, and nearly-absent stem. It appears between October and early April across North America, and features a brown oyster-shaped cap and its color range from white to gray. A number of similar species are closely related, including Pleurotus pulmonarius (which is often paler, and appears between late April and September), and Pleurotus populinus (which is found on the wood of quaking aspen). It can be described as a fan-like or a broad oyster-shaped cap . The gills are white to cream in color while the flesh is white, stiff and differ in thickness with stipe arrangement. It has the bittersweet aroma of benzaldehyde, which is a characteristic of bitter almonds. These mushrooms growth by two phases which is called vegetative or mycelial. In the P. ostreatus growth, after spore germination of in vitro-grown mycelia, hyphae (microscopic filaments) will invade the substrate. Hyphae continue to grow and branch to form a network of hyphae. Mycelial growth is generally conjugated with increased respiration and enzyme production. Before completing hyphal invasion, hyphae absorb digestive products then penetrating the substrate. The vegetative growth provide the nutritive materials required for the mushroom growth by direct contact with the substrate (figure 2). Pleurotus ostreatus is also known as carnivorous mushroom because its mycelia can kill and digest nematodes (small roundworms). The mushroom acts as a primary decomposer of wood and beech trees due to its sapotrophic nutrition. They actually benefit the forest by decaying the dead wood, returning essential elements and minerals to the ecosystem in a form useful to other plants and organisms (figure 2). It is usually been found in temperate subtropical forests around the world but it is absent from the Pacific Northwest of North America. Other uses of these mushrooms, they can help your body as well. A study showed that they produce lovastatin, which is a cholesterol lowering drug and the consumption of their extracts lowered cholesterol levels in a person. The role in mycorestoration process is very fascinating as it is used to lessening pollution levels in certain areas. Oyster mushrooms are also efficient in breaking down organic bonds in toxic chemicals, petroleum products, paper and coffee grounds. These mushrooms also contain little amounts of arabitol, a sugar alcohol, which can cause gastrointestinal upset in some people. Other than that, they are widely cultivated and used in India, the Republic of Czech and Slovak where they are used to cook a variety of dishes such as stir-fried dishes, stews and soups. Cultivated oyster mushrooms are not only taste sweet but varied, because they can be used as a delicate flavoring agent in many ways. The economic importance of the mushroom mainly use as food for human consumption. It has most of the mineral salts needed by the human body such as niacin, vitamin C, vitamin B complex and protein. The niacin content is ten times higher than any other vegetables. It is very suitable for people that are having hyperacidity and constipation because of the alkaline ash and high fibre content. It has 1.6 – 2.5% protein content. The folic acid present in oyster mushrooms also helps to heal anemia. People with high blood pressure, diabetes and obesity is very suitable to take this mushroom due to its calorific value, low sodium : potassium ratio, starch, and fat. The manufacture of Pleurotus species accounts 25% of total world production. Thus, they are the second most essential mushrooms in the world. It contributes nearly 85% of the total world production and are cultivated worldwide especially in China as the world leader in Oyster production. Apart from that, Korea, Japan, Italy, Taiwan, Thailand and Phillipines also producing oyster mushrooms. Some species can be cultivated on straw or newspaper and other media. Some of the Pleurotus species are Pleurotus citrinopileatus (golden oyster mushroom), Pleurotus cornucopiae (branched oyster mushroom), Pleurotus eryngii (king trumpet mushroom), and Pleurotus ostreatus (oyster mushroom). The number of people who are getting interested into this field is quickly increasing. Species of Pleurotus are cheapest and easiest to grow among all the cultivated edible mushrooms. Cultivation does not require complex substrate preparation technique. It has faster growth rate and early cropping. About 5 to 6 crops can be taken in a year as the total cropping period is 60 days. Oyster mushroom cultivation is continuous business where different natural resources can be used as a growing material. The expectation to create a practicable business in urban environments by using coffee grounds is attractive for a lot of entrepreneurs. The time to learn mushroom cultivation is time consuming and costly. Due to this reason there are many companies in Europe specialized in mushroom cultivation that are offering training for entrepreneurs and organizing events to build community and share knowledge. They also show the positive impact of this business on the environment. Most farmers also learned mushroom cultivation by doing since mushroom cultivation is not a subject obtainable at school. For do-it-yourselfers, oyster mushrooms can be grown from kits sold through seed catalogues and gardening magazines at home or office in a small scale. In conclusion, mushrooms are a rising crop with unique and highly desired product and offer many benefits. Its economic importance to human, in terms of medical uses and commercial cultivation have great impact to the environment. With a bit of practice, oyster mushrooms can easily be grown on many different substrates including straw, newspaper, and more in a variety of locations.