The provided video tells you all about the development of limbs, its different stages along with pictorial representation making it easier for you to grab the concepts. Timeline : 0:09:introduction 1:06:evolutionary history 1:20:major structures of limb 1:47:mechanism of limb development 3:06:skeletal elements 6:27:bud emergence and growth 9:10:somitogenesis 18:13:bmp signaling 20:49:major signaling system 21:20:summary