Chloroplast
The Chloroplast is the primary organelle where Photosynthesis occurs in plants and algae. It consists of several key structures: the outer membrane, inner membrane, Stroma, and Thylakoid membranes. The Grana (stacks of thylakoids) contain Chlorophyll and other Pigments that absorb light for the Light-Dependent Reactions. Chloroplasts are believed to have originated from a symbiotic relationship between ancestral eukaryotic cells and photosynthetic prokaryotes, as explained by the Endosymbiotic Theory.