1. Photosphere: The photosphere is the innermost and visible layer of the sun's atmosphere. It is where the majority of the sun's visible light is emitted. The photosphere is characterized by granules, which are bright and dark patches caused by convection currents of hot and cooler gases.

2. Chromosphere: The chromosphere is a thin layer that lies just above the photosphere. It is characterized by a reddish color and prominent spicules, which are jets of hot gases that rise and fall back into the chromosphere.

3. Transition Region: The transition region is a narrow layer between the chromosphere and the corona. It is where the temperature rapidly increases from about 20,000 Kelvin in the chromosphere to over a million Kelvin in the corona.

4. Corona: The corona is the outermost layer of the sun's atmosphere. It extends millions of kilometers into space and is best observed during solar eclipses. The corona is extremely hot, with temperatures ranging from a few hundred thousand to several million Kelvin. It is also the source of the solar wind, which is a constant stream of charged particles emitted by the sun.

Additionally, there are two more structures observed in the outermost layers of the sun's atmosphere:

5. Prominences: Prominences are large, arched loops of ionized gas that extend from the surface of the sun and into the corona. They are often bright and are sometimes referred to as solar flares.

6. Coronal Holes: Coronal holes are regions in the corona where the density of plasma is lower, making them appear darker than the surrounding areas. Coronal holes are the sources of fast solar wind streams.