A ""little peep at the hidden world of life in the womb"" is how its author modestly describes this delightful, informative work. For Vaughan, formerly a writer at the National Institutes of Health and currently biomedical sciences editor at Cambridge University Press, writing this book combined professional and personal interests--his first child was conceived the week the book contract was signed. His enthusiasm for the task shows, for there isn't a dull paragraph in any of its nine month-by-month chapters. Their titles give a hint of Vaughan's style: The first one is ""Sex and the Single Cell""; the final one is ""Partum Is Such Sweet Sorrow."" While occasionally verging on terminal cuteness, the text is overall a masterpiece of clear writing, making science not just comprehensible but entertaining. Chapters open with brief sections describing the appearance and physical status of the embryo or fetus at successive stages of development. These straightforward, factual bits are followed by more freewheeling essays. For the fifth month, for example, he considers how the brain develops, the role that REM sleep may play in this, the possible roots of dyslexia and schizophrenia, even the potential effects of maternal stress hormones. For the seventh month, he gives a fascinating account of how prenatal experience prepares the fetus's senses for life in the outside world. In the last chapter, Vaughan discusses how the baby's brain monitors its development and sends out the signals to begin labor. While having special interest for parents-to-be--it would make a great girl for them--this should appeal to anyone with a speck of curiosity about how he or she came to be.