My must have for summer. started using when I had blonde hair, to keep it looking fresh. it can either be used while sitting in the sun, for the natural lightening effect, or it can be used with heat, for extra lightening effect. I have used it for both. I spray it on before blowdrying, the blow its in small sections, so the heat can really activate it and then flat iron too. a good product to used to lighten up hair in summer, and overall to keep highlights looking light and not dull and brassy