C. elegans is maintained in the laboratory on Nematode Growth Medium (NGM) agar which has been aseptically poured into petri plates. The NGM agar medium can be poured into petri plates easily and aseptically using a peristaltic pump. This pump can be adjusted so that a constant amount of NGM agar is dispensed into each petri plate. A constant amount of agar in the plates reduces the need for refocusing the microscope when you switch from one plate to another.For imaging purposes, low peptone NGM is prepared which contains less concentration of bactopeptone as compared to the normal NGM. This is because we don't want the seeded bacteria to grow too much and obscure the images, rather just sufficient enough to keep the worms from crawling out of the plate due to lack of food. The imaging plates can be 35mm, 60mm or 90mm in diameter depending on the assay design.