During the early stages of development, the primitive streak is the structure that will establish bilateral symmetry, determine the site of gastrulation and initiate germ layer formation.

During gastrulation, some of the cells migrating inward contribute to the mesoderm, an additional layer between the endoderm and the ectoderm.

During gastrulation, some of the cells migrating inward to form the endoderm form an additional layer between the endoderm and the ectoderm.

During this stage of the cell cycle this makes the individual chromosomes in many cells visible by optical microscope.

During operation of electrochemical cells, chemical energy is transformed into electrical energy and is expressed mathematically as the product of the cell's emf and the electric charge transferred through the external circuit.

During the fermentation process, yeast cells in the must continue to convert sugar into alcohol until the must reaches an alcohol level of 16 %– 18 %.

During these stages, two centrosomes, containing a pair of centrioles in animal cells, migrate to the two poles of the cell.

During this time disjunction occurs, which is one of the processes leading to genetic diversity as each chromosome can end up in either of the daughter cells.

During embryonic development, cells are restricted to different layers due to differential affinities.

During normal calcification, a major influx of calcium and phosphate ions into the cells accompanies cellular apoptosis ( genetically determined self-destruction ) and matrix vesicle formation.

During organogenesis, molecular and cellular interactions between germ layers, combined with the cells ' developmental potential, or competence to respond, prompt the further differentiation of organ-specific cell types.

During the process of epithelial differentiation, cells become cornified as keratin protein is incorporated into longer keratin intermediate filaments.

During the early Silurian, they developed specialized cells, which were lignified ( or bore similar chemical compounds ) to avoid implosion ; this process coincided with cell death, allowing their innards to be emptied and water to be passed through them.

During morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells.

During a sharp wave, as many as 5 – 10 % of the neural population may emit action potentials during a period of 50 ms ; many of these cells emit bursts of several action potentials.

During embryological development, new capillaries are formed by vasculogenesis, the process of blood vessel formation occurring by a de novo production of endothelial cells and their formation into vascular tubes.

During the brain development, reelin is secreted in the cortex and hippocampus by the so-called Cajal-Retzius cells, Cajal cells, and Retzius cells.

During exercise, the water level retracts due to the increase in concentration of lactic acid in the muscle cells.

During plasma donation, the red blood cells are pumped back into the body right away and only the plasma is collected.

During each heartbeat, a healthy heart will have an orderly progression of a wave of depolarisation that is triggered by the cells in the sinoatrial node, spreads out through the atrium, passes through the atrioventracular node and then spreads all over the ventricles.

During gestation, the cells of the primordial gonad that lie along the urogenital ridge are in a bipotential state, meaning they possess the ability to become either male cells ( Sertoli and Leydig cells ) or female cells ( follicle cells and Theca cells ).

During the next stage, cleavage, mitotic cell divisions transform the zygote into a tiny ball of cells, a blastula.

During treatment, Race reportedly would go into trance and undergo a personality change, becoming fluent and articulate, and giving diagnosis and prescription for his own disease as well as those of others.

During this early epoch, galaxies undergo a major burst of star formation.

During this period, Kipsigis males undergo three main traditional ceremonies called the kelab-eun, the tyenjinet and the kayaet.

During this process, the radionuclide is said to undergo radioactive decay, resulting in the emission of gamma ray ( s ) and / or subatomic particles such as alpha or beta particles.

During oestrus, females undergo a swelling of the perineal tissue lasting 10 to 20 days.

During the perimenopause years, many women undergo noticeable and clinically observable physical changes resulting from hormonal fluctuations.

During infancy, subjects should undergo therapies to improve muscle tone.

During that they may undergo coalescence or aggregation.

During the days before the sacrifice, both gods undergo purification.

During the British rule the district was at peace and did not undergo any major political changes.

During the active part of their day, animals that undergo daily torpor maintain normal body temperature and activity levels, but their temperature drops during a portion of the day ( usually night ) to conserve energy.

During this period he had to travel through the Hadramaut and Rub ' al Khali deserts, and tasted coffee in Mocha, being most probably the first European to undergo such experiences.

During their transit in the epididymis, sperm undergo maturation processes necessary for them to acquire these functions.

During the next 14 days in the case of P. falciparum, the liver-stage parasites differentiate and undergo asexual multiplication, resulting in tens of thousands of merozoites which burst from the hepatocyte.

During Year 10 ( age: 15 – 16 ) chanichim undergo a ' hadrachah ' ( leadership ) course.

During the larval stage, mealworms will undergo repeated molting between bouts of eating various vegetation or dead insects.

During the fifth ( 1979 – 80 ) season, Julie gets married and later moves to Houston with her pilot husband Max Horvath ( Michael Lembeck ); this plot device was written in so that Mackenzie Phillips could undergo drug rehabilitation.

During the afternoon of September 10, Hurricane Luis began to undergo an extratropical transition as it rapidly approached the Canadian coastline.

During the ceremony, the Pollywogs undergo a number of increasingly embarrassing ordeals ( wearing clothing inside out and backwards ; crawling on hands and knees on nonskid-coated decks ; being swatted with short lengths of firehose ; being locked in stocks and pillories and pelted with mushy fruit ; being locked in a water coffin of salt-water and bright green sea dye ( fluorescent sodium salt ); crawling through chutes or large tubs of rotting garbage ; kissing the Royal Baby's belly coated with axle grease, hair chopping, etc.

During meiosis, unstable repeats can undergo triplet expansion ( see later section ); in this case, the germ cells produced have a greater number of repeats than are found in the somatic tissues.

During the summer monsoon, wind patterns undergo large scale changes.

During the 1950s, the base would undergo many changes and would change hands from TAC to the Strategic Air Command ( SAC ).

During the spring of 2010, Barth was forced to undergo emergency back surgery.

During the recovery period of neurapraxia, it is essential that the joints constantly undergo passive movement in order to preserve proper mobility.