<span> a </span>girl's<span> breasts may start to grow, but she may not get her period until years later. You may continue to go through </span>puberty<span> changes until you're 20 years old.</span>
<h3>Origin of cell.</h3>
In 1665,an english scientist Robert Hooke designed his own microscope and examined a cork from a bark of tree.He observed that cork is made up of many boxes like units which were packed together .He called these units <u>Cells</u>.
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