Cancer research. Image 2 of 2. Cancer cells. Scanning electron micrograph (SEM) of precancerous (neoplastic) cultured cells for comparison with normal cells (see in M133/145). This cell culture was exposed to a cancer-causing chemical to test the chemical and to study its effects on cell cultures. The cells here have been dividing and growing more rapidly, and the growth is irregular in structure, which is typical of cancerous growth. Scanned in the Health and Pollutants Laboratory of the INRS (the French National Institute of Research and Safety), Nancy, France. Tests are carried out here to establish the toxicity and cancer-causing properties of different materials, chemicals and pollutants.