A stem cell–derived human embryo model at a developmental stage equivalent to that of a day 14

A stem-cell derived human embryo model showing blue cells (embryo), yellow cells (yolk sac) and pink cells (placenta).

By James Gallagher

Health and science correspondent

Scientists have grown an entity that closely resembles an early human embryo, without using sperm, eggs or a womb.

The Weizmann Institute team say their "embryo model", made using stem cells, looks like a textbook example of a real 14-day-old embryo.

It even released hormones that turned a pregnancy test positive in the lab.

The ambition for embryo models is to provide an ethical way of understanding the earliest moments of our lives.

The first weeks after a sperm fertilises an egg is a period of dramatic change - from a collection of indistinct cells to something that eventually becomes recognisable on a baby scan.

This crucial time is a major source of miscarriage and birth defects but poorly understood.

"It's a black box and that's not a cliche - our knowledge is very limited," Prof Jacob Hanna, from the Weizmann Institute of Science, tells me.

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