We still know very little about exactly how the embryo forms out of a mass of dividing cells in those crucial first weeks after conception. This is also the time when many miscarriages occur, and scientists want to understand why. Couples going through IVF donate spare embryos for research and scientists are permitted to study them in a test tube, or in vitro, allowing them to grow and develop for up to 14 days. This 14 day rule is abided by globally, and it’s enshrined in the Human Fertilisation and Embryology Act in the UK. Thirty years ago no-one could keep these embryos alive for more than a few days but recently the techniques have moved on and they have been cultured for nearly 14 days. So should the 14 day rule be extended? Gaia Vince discusses this question with bioethicist professor Insoo Hyun of Case Western University and Harvard Medical School. There are other ways of studying this early development that don’t involve growing an actual embryo, and that’s by using just a few stem cells from it. These are cells that haven’t yet specialised into any type of body cell and so they have the potential to become any cell type. Researchers can grow these cells into structures that resemble embryos, although they could never survive inside a woman’s womb, and these artificial embryos aren’t subject to the 14 day rule. Gaia talks to Dr Naomi Moris of the Crick Institute in London about her work on what she calls gastruloids. Whaling was a huge industry in the 19th century, and populations of sperm whales plummeted, as hunters sought the oil in their heads that was used everywhere for lighting. The whalers who were hunting in the North Pacific kept meticulous records that have been recently made public. Biologists have been studying them, and picking out unexpected changes in the patterns of whale capture. Dr Luke Rendell of St Andrews University explains how he and his colleagues worked out that that the whales seemed to be learning from each other how to avoid the boats. A piece of intricate Ancient Greek engineering called the Antikythera mechanism, that was found by sponge divers in 1901 in the Mediterranean, has fascinated many people. Last week a team from University College London published the latest explanation of how the device worked. Science writer Jo Marchant herself became so obsessed with the mechanism that she published a book on it called Decoding the Universe and she talks to Gaia about the object and what the new research tells us about how the Greeks understood the cosmos two thousand years ago.