The present invention provides improved methods of injecting an avian egg containing an embryo, preferably an early embryo (e.g., a blastoderm). The methods of the invention may be used to deliver a substance to an egg, remove a sample from an egg, and/or to insert a detector device into an egg to collect information therefrom. In preferred embodiments, the invention is used to deliver a substance to the embryo in ovo. In other preferred embodiments, the invention is used to produce chimeric or transgenic avian embryos in ovo.