HeLa cells are a cell line.

Cell culture is a laboratory process that involves growing cells from humans, animals, or insects in a controlled environment. The cells can come from multicellular eukaryotes, established cell lines, or established cell strains.  Cell culture involves growing cells in tissue culture flasks in a medium containing cell nutrients and growth factors. The cells are grown in an incubator under controlled conditions to provide enough material for testing.  In 1885, Wilhelm Roux established the cell culture principle for growing animal cells. In his experiment, he removed and maintained a portion... Show more

Cell culture is a laboratory process that involves growing cells from humans, animals, or insects in a controlled environment. The cells can come from multicellular eukaryotes, established cell lines, or established cell strains. 

Cell culture involves growing cells in tissue culture flasks in a medium containing cell nutrients and growth factors. The cells are grown in an incubator under controlled conditions to provide enough material for testing. 
In 1885, Wilhelm Roux established the cell culture principle for growing animal cells. In his experiment, he removed and maintained a portion of the medullary plate of an embryonic chicken in warm saline solution.

Some parameters for healthy cells include:
Nutrient supply
Flow and shear stress
Carbon dioxide (CO2) levels and pH of the medium
Temperature
Humidity 

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