NOTE: YouTube demonstrates perfectly what is both a strength and weakness of the Internet: the fact that anyone can post videos. Since anyone can post, the quality and scholarly acceptability of videos varies greatly. There may be useful video clips on YouTube, but you must evaluate them for authority and relevance. Before referencing any material from YouTube (or other video sites on the Internet) in a paper or presentation, it is highly advisable to check with your instructor concerning the acceptability of the video for the assignment.
Try searching terms such as microscope, biology lab, or biotechnology to start exploring this resource.