Four cubes is a fairly simple design, and the instructions are freely available through David Mitchell’s website. My recollection about this one, is that I was at an origami convention, and someone showed me David Mitchell’s website, and the next minute I produced this thing. I clearly thought this was really easy stuff, because I felt the need to make it super tiny. I believe it is less than 2 cm across.
I checked the date on this photo, and clearly my memory is completely fabricated, as I did not go to an origami convention that year.