Cell cultures. Gloved hands manipulate glass cover slips in multi-well sample trays containing cell cultures. Forceps are being used to lower a cover slip into one of the sample vials. Cell cultures are used in the laboratory to study cell growth, and to test the effects of substances on the cells, such as drugs. The cover slips are being added so that some cells attach to it, and they can then be studied under a microscope. Here, the cells are neuroblastoma cells, which are cancerous cells of nervous tissue.