A plastid is a membrane-bound organelle found in plants, algae and other eukaryotic organisms that contribute to the production of pigment molecules. Most plastids are photosynthetic, thus leading to color production and energy storage or production. There are many types of plastids in plants alone, but all plastids can be separated based on the number of times they have undergone endosymbiotic events. Currently there are three types of plastids; primary, secondary and tertiary. Endosymbiosis is reputed to have led to the evolution of eukaryotic organisms today, although the timeline is highly debated.