Google has a YouTube channel for educators: this is a great place to find current, engaging, and short videos that can explain or discuss a myriad of topics.
As an example, here is one on the topic of How Small is an Atom? It is less than five minutes (good!) and very informative. As an added bonus, it’s entertaining – note the captioning!
As you approach a new term in search of course materials that are recent and relevant, try looking at the YouTube for Teachers channel.