Engelmann studied the effect of different region of the visible spectrum on the rate of photosynthesis of different algae with use of aerobic bacteria. The amount of oxygen released was found to be maximum in blue and red absorption bands of chlorophyll. Red drop was discovered by Emerson,
Von Helmont had claimed origin of mice from human sweat and wheat bran kept in dark for 21 days.
Lavosier identified that CO2 that and O2 involved in photosynthesis and respiration.