Mushrooms are a group of fleshy saprophytic fungi that are found growing on dead organic matter. Over 10,000 species of mushrooms are believed to be found naturally growing in moist, damp forests and soils rich in organic matter throughout the world. Among these, some are edible while others are toxic. A few species of mushrooms are known for their medicinal properties as well and hence they are known as medicinal mushrooms. A mushroom initially forms a minute fruiting body during its initial developmental stages. This fruiting body is called a pin because of its small size and this developmental stage is known as pin-stage. Later when these pins grow in size, they are called buttons. This stage during mushroom development is known as button-stage. Once buttons are formed, mushrooms grow or expand rapidly into enlarged fruiting bodies and caps. Some mushrooms expand overnight while others grow slowly. Edible mushrooms are often grouped along with vegetables and known as 'Meat of the Vegetable World'.