1) "The Main Steps of photosynthesis are compartmentalized into different regions of the chloroplast: Thylakoid menbrane and compartment: The light reactions take place in the thylakoid membrane and thylakoid compartment and are concerned with the initial conversion of light energy into chemical energy stored in ATP and NADPH. The NADPH and the ATP feed into the Calvin cycle in the Chloroplast stroma where the ATP provides energy for molecular rearrangements and the electrons and hydrogen ion carried by the NADPH are transfered to the organic molecules involved in the Calvin cycle. Stroma. The Dark reactions, mainly the Calvin cycle take place in the substance surrounfing the thylakoids. In the Calvin cycle, carbon from carbon dioxide is brought into the cycle as a source of carbon. Then after a series of molecular rearrangements, in part powered by ATP, the electrons and hydrogen ions from the NADPH produced in the light reactions are added to the molecules in the Calvin cycle yielding the three carbon phosphate sygar, PGAL. The PGAL is used to make glucose and other carbohydrates for the plant." Source and further information: http://staff.jccc.net/PDECELL/photosyn/thylakoid.html 2) "Stroma, the thick fluid found in between grana, which are stacks of thylakoid disks. Stroma is where the carbohydrate formation reactions occur in the chloroplast of plant cells undergoing photosynthesis." Source and further information: http://en.wikipedia.org/wiki/Stroma "A Thylakoid is a membrane-bound compartment inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. The word "thylakoid" is derived from the Greek thylakos, meaning "sac". Thylakoids consists of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thylakoids frequently form stacks of disks referred to as "grana" (singular: granum). "Grana" is Latin for "stacks of coins". Grana are connected by intergrana or stroma thylakoids, which join granum stacks together as a single functional compartment." Source and further information: http://en.wikipedia.org/wiki/Thylakoid