Over on macOS, you can pack a single text file or a zip file (an archive full of files of any type) into an image. First, move the files in question to the desktop. Again, we're calling the container image "picture.jpg and the hidden file "secret.txt," although in this case, it could just as easily be "secret.zip." Then launch the Terminal app (open Spotlight with Cmd+Space, type "terminal," and select the correct app when it appears). In Terminal, type "cd desktop" and hit Enter to switch to the desktop. Next, type "cat picture.jpg secret.txt > hidden.jpg" and hit Enter. As on Windows, we're calling the finished image "hidden.jpg," but you can change the file name to whatever you'd like. When you open it in any image editing program, it will appear to be a normal picture; when you open it in an app like TextEdit, the hidden text will appear at the end. If you've hidden an archive, you retrieve the hidden files slightly differently: Go back to the Terminal, type "unzip hidden.jpg" (or whatever file name you chose), and hit Enter. The hidden files will then spill out onto the desktop once more.