Chick embryos have been used for the developmental study of vertebrates. However, the continuous and long-term observation of the same embryo is difficult, because development tends to be interrupted when a large window is made through the eggshell. To overcome this problem, the authors of this video established a continuous observation system for developing chick embryos. In this system, a window is made through the eggshell for observation, and then the egg is returned to the incubator. Time-lapse video images are taken and re-constituted into an animation. Fertilized white Leghorn chicken eggs (Miyake Hatchery, Inc., Japan) were incubated at 37.7oC in a humidified incubator (p-008; Showa Furanki, Inc., Japan) for 2 days. A shell cap with a diameter of 3 cm at the sharp end of each egg was cut out with a file to make a window, and the hole was sealed immediately with poly-vinylidene-chloride film (Asahi Kasei Home Products Corporation, Japan). The eggs were then incubated again under illumination for 18 days. Images were taken every hour by a video microscope (VH-5000C; Keyence, Japan) and assembled into an animation.