Before Pasteur's experiments using beef broth and flasks with S-shaped tubing, most people thought that new cells formed by

spontaneous generation

Explanation:

Spontaneous generation is the idea that living organisms arise from nonliving matter. Louis Pasteur was a French chemist who designed a series of experiments to determine whether a sterile nutrient broth could spontaneously generate microorganisms. He added nutrient broth to two flasks, curved their necks into S shapes, and finally boiled the broth to eliminate any potential microorganism. Pasteur did not observe any microorganisms in the flasks with the S-shaped necks, thereby showing that microorganisms present in the air were responsible for contaminating nonliving material and thus rejecting the idea of spontaneous generation.

carbon atoms, hydrogen, oxygen, and nitrogen.

sex cells are usually half's then they find another half and make a fertilize egg