Those molecules are stored in the stroma of the chloroplast before they are used in photosynthesis.

Where they are stored

In plant cells, photosynthesis happens inside chloroplasts, which have internal stacks of membranes called thylakoids surrounded by a fluid-filled area called the stroma. The main carbohydrate made by photosynthesis (in the form of glyceraldehyde 3-phosphate that becomes glucose) is often stored as starch granules in the stroma of the chloroplast until the plant needs it. Other sugars can be converted and moved to different parts of the cell for use or longer-term storage.

Light vs. dark reaction locations

  • The light-dependent reactions (that make ATP and NADPH) occur in the thylakoid membranes.
  • The Calvin cycle (light-independent reactions that fix carbon dioxide into sugars) occurs in the stroma, where the enzymes and stored carbohydrate (starch) are found.

So, if your question refers to where the products of photosynthesis are kept inside the organelle before being used, the answer is that they are stored mainly as starch in the stroma of the chloroplast.

Information gathered from public forums or data available on the internet and portrayed here.