To investigate the effects of gravity on morphogenesis at the cellular level, we have proposed a new experimental system with micromeres from sea urchin embryos [Izumi-Kurotani, A., Kiyomoto, M. Morphogenesis and gravity in a whole Amphibian Embryo and in isolated blastomeres of sea urchins, in: Marthy, H. -J. (Ed.), Developmental Biology Research in Space. Adv. Space Biol. Med. vol. 9, Elsevier, Amsterdam, pp. 83-99, 2003]. We studied spicule formation in cultured micromeres of sea urchin embryo under various conditions of gravity: hypergravity by a centrifuge and simulated microgravity in a vertical clinostat. Spicule elongation was suppressed under both experimental conditions. (C) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.