https://joy.videvo.net/videvo_files/video/free/2020-04/large_watermarked/200401_Microscope%205_04_preview.mp4 Scientist Operating a Microscope 02 Operating the focus knobs of a laboratory microscope. biochemistrybiologychemistrycoll_vaccinefocusfocussinginstrumentlablaboratorymicroscopepharmapharmaceuticalsresearchsamplesamplessciencescientificscientisttechnician