During pregnancy, these painless tightenings are called Braxton Hicks contractions. When you are having regular, painful contractions that feel stronger and last more than 30 seconds, labour may have started. As labour gets going, your contractions tend to become longer, stronger and more frequent. During a contraction, the muscles in your womb contract and the pain increases.
During initial stages of assimilation, Borg nanoprobes began attaching themselves to the victim's red blood cells, allowing them to circulate throughout the body. (VOY :  Scorpion ) Within minutes, the nanoprobes spread visibly through the capillaries of the victim's skin.
Jean Piaget coined the term assimilation to describe the process for how we add information or experiences into our existing structures of knowledge or schemas. As we blend the existing information with the new we expand or modify our schemas but we don't fundamentally change the way the schema is organized.