Assays are sometimes under-appreciated for their important role in cell therapy laboratories. They are used to characterize the product, whether as the starting raw material or the final product infused to the patient. Assays range from automated cell counting, performed by most labs, to use of a multisizer cell counting instrument, required by some complex cell culture processes. This session will discuss some of the assays commonly performed in most cell therapy laboratories and stimulate interest in the under-appreciated, taken-for-granted area in cell therapy product manufacturing.