Here is an example of a quick slideshow/movie created using the movie maker tool in Google Photos:
This movie was created on an Android phone. Here is a tutorial video showing exactly how it was made. Up until just recently, you could only make these movies using a mobile device – an Android phone/tablet or an iPhone or iPad. Recently I’ve noticed the feature is now available on the Web version of Google Photos and this article will tell you exactly how to use it. I haven’t seen an official announcement, and I still find it a little buggy, but it does work and I expect it will get better.