As for indoor growing, there is no sunlight, what you need now is artificial light such as HID, HPS and LED grow light
LED grow light is the newest generation of grow lighs, having advantages compared with HID and LED
1.LED is more efficient, it can save about 30% engergy , compared with HID or HPS
2.the spectrums are good, always full spectrum, with higher red and blue lights, which are good for photosynthesis, helping your cannabis grow faster
3. nature, about the heat, what plants like is the energy carried by solar light. The energy contains heat.
If we give cannabis the light they desire, the energy is enough for them to grow
Actually, too much heat is not good, it may burn the leaves of the plants