Plants use carbon dioxide (CO2) and water (H2O) during photosynthesis to make sugars and starches.

Here's how it works:

* Light energy from the sun is captured by chlorophyll in the plant's leaves.

* This energy is used to split water molecules (H2O), releasing oxygen (O2) as a byproduct.

* The energy is also used to combine carbon dioxide (CO2) from the air with the hydrogen (H) from the split water molecules.

* This process creates simple sugars (like glucose) which can be used directly by the plant for energy or converted into complex starches for storage.

So, the key ingredients for photosynthesis are sunlight, water, and carbon dioxide.