NIH recommendations: embryos (14) 18 days or older are not acceptable. Unacceptable procedures: transfer human embryos to animals for gestation; transfer research embryos or parthenotes (unfertilized eggs) to humans; separation of blastomeres for generating twins; cloning by nuclear transplantation; creation of any type of chimera (human–human, human–animal); creation of embryos in the lab from stem cells; cross-fertilization by human gametes with the exception of clinical laboratory sperm penetration tests with animal eggs; embryo transfer to cavities other than the uterus; sex selection with the exception of preventing sex-chromosome-linked disease; use of sperm or egg without consent; use of sperm or egg from donor who was paid more than reasonably expected. The embryo research policies vary in different countries, and may/may not permit the use of embryos/tissues for studying infertility, contraception, genetic screening, gene therapy, cloning, construction of chimeras, interspecific implantation, sex-selection, etc. Embryo culture and embryo transfer had minimal effects on postnatal growth when compared with in vivo development with an equivalent litter size in mice. However, embryo culture, and to a lesser extent embryo transfer, led to an enhanced systolic blood pressure at 21 weeks compared with in vivo development independent of litter size, maternal origin, or body weight. Moreover, activity of enzymatic regulators of cardiovascular and metabolic physiology, namely, serum angiotensin-converting enzyme and the gluconeogenesis controller, liver phosphoenolpyruvate carboxykinase, were significantly elevated in response to embryo culture and/or embryo transfer in female offspring at 27 weeks, independent of maternal factors and postnatal growth (Watkins AJ et al 2007 Proc Natl Acad Sci USA 104:5449).  stem cells,  ART,  phosphoenolpyruvate,  gluconeogenesis,  angiotensin