Angiotensin ii stimulates vasoconstriction, whereas stimulates vasodilation.

The hormone responsible for stimulation of vasodilation is epinephrine or adrenalin.  

Widening of blood vessels is called vasodilation. It increases blood flow thorough blood vessels. Increase in the blood flow provides more oxygen and nutrients such as glucose and lipids to the body tissues in case of nutrient shortage or insuffient blood supply to the cells. Vasodilation occurs in response to hormones or the nervous system.  

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.