Phytoplankton are tiny, microscopic plants that float in the ocean and other bodies of water. They are a crucial part of the aquatic food chain, serving as the primary food source for many marine animals, including zooplankton and small fish. These organisms use sunlight to produce energy through a process called photosynthesis, just like land plants. In addition to being a food source, phytoplankton play a vital role in our planet's ecosystem. They absorb carbon dioxide and release oxygen, helping to regulate the Earth's atmosphere. This makes them essential for maintaining a healthy environment, supporting both marine life and human beings.