Here's why:

* Plants: The most well-known examples of photosynthetic organisms. They use sunlight, water, and carbon dioxide to produce their food (sugars) and release oxygen as a byproduct.

* Algae: These are simple, aquatic organisms that come in many forms (from single-celled to large seaweed). They also use photosynthesis to produce their own food.

* Some bacteria: Certain types of bacteria, called cyanobacteria, are able to perform photosynthesis. They are often found in aquatic environments and contribute significantly to the oxygen in our atmosphere.

Let me know if you'd like to know more about the process of photosynthesis itself!