1 Granum 2 Chloroplast envelope 3 Thylakoid 4 Stromal thylakoid 5 Stroma   ◄ You are here 6 Nucleoid (DNA ring) 7 Ribosome 8 Plastoglobulus 9 Starch granule Stroma, in botany, refers to the colorless fluid surrounding the grana within the chloroplast.

[1] Within the stroma are grana (stacks of thylakoid), the sub-organelles where photosynthesis is started[2] before the chemical changes are completed in the stroma.

In the first stage, light-dependent reactions capture the energy of light and use it to make the energy-storage molecules ATP and NADPH.

The series of biochemical redox reactions which take place in the stroma are collectively called the Calvin cycle or light-independent reactions.

There are three phases: carbon fixation, reduction reactions, and ribulose 1,5-bisphosphate (RuBP) regeneration.