Nematodes, commonly known as roundworms, are a diverse group of unsegmented worms found in various environments, including soil, freshwater, and marine habitats. They play essential roles in ecosystems, such as decomposing organic matter and serving as a food source for other organisms. Some nematodes are beneficial, while others can be harmful pests to plants and animals. These microscopic creatures have a simple body structure, typically featuring a cylindrical shape and a tough outer cuticle. Nematodes are incredibly abundant, with millions of species identified, and they can adapt to extreme conditions, making them a fascinating subject of study in ecology and agriculture.