This article is very outdated. Small brushless quadcopters are readily available now. Such as the Hoverbot Nano [1] mentioned in another commment, or a Eachine

This article is very outdated. Small brushless quadcopters are readily available now. Such as the Hoverbot Nano [1] mentioned in another commment, or a Eachine Lizard [2], and lots more. And you can go even smaller, such as a pepperfish [3] This is a small brushless quad with 0703 motors with a 1 cell battery. https://i.imgur.com/EdFFfsc.png https://i.imgur.com/EdFFfsc.png / http://rotaro.no http://rotaro.no 54mm in diameter [1] https://hoverbot.io/ https://hoverbot.io/ [2] https://www.banggood.com/Eachine-Lizard95-95mm-F3-FPV-Racer-BNF-4-in-1-10A-ESC-OSD-5_8G-48CH-25MW100MW-VTX-600TVL-Camera-3S-p-1141589.html https://www.banggood.com/Eachine-Lizard95-95mm-F3-FPV-Racer-... [3] http://fishpepper.de/projects/pepperf1sh/ http://fishpepper.de/projects/pepperf1sh/