The majority of the gardens in the world grow plants. However, there are some gardens that emphasize animal farming as well. These are called zoological gardens and are more commonly known as zoos. The most common form of a garden is a residential garden. These adjoin houses and residential areas. As many people derive a portion of their daily diet from a residential garden, it is also called a kitchen garden. Gardens built for commercial and industrial purposes are also common. Modern gardens can either rely on technology and scientific advancements, or be completely organic and eco-friendly. Following the basic principles of organic agriculture and organic horticulture, one can easily start an organic garden. In many cases, expenses are also minimized as costly chemicals like toxic insecticides and synthetic fertilizers are replaced by organic, healthier substitutes like biological manure and natural compost. Organic gardening involves numerous thoughtful processes such as biodynamic farming, companion planting, integrated pest management, composting, and pheromone traps.