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Scientists Develop Model Human Embryo Without Egg or Sperm

In a ground-breaking achievement, scientists at the Weizmann Institute have successfully grown an entity that closely mimics an early human embryo, all without the use of sperm, eggs, or a womb. This “embryo model” created using stem cells bears a striking resemblance to a real 14-day-old human embryo and even releases hormones capable of triggering a positive pregnancy test in a laboratory setting.

Why Embryo Models Matter

Understanding the first few weeks following fertilization, from a collection of undifferentiated cells to the development of recognizable structures, is crucial. This period is marked by rapid changes and is a significant source of miscarriages and birth defects, yet it remains poorly understood.

Embryo research has long been a complex, ethically sensitive field. However, researchers are now exploring innovative approaches to replicate natural embryo development. This recent study, published in the journal Nature, represents a significant milestone—the creation of a “complete” embryo model that faithfully replicates key early embryo structures.

How Did They Do It?

Rather than using traditional sperm and egg, the scientists utilized naive stem cells that were reprogrammed to possess the potential to differentiate into any type of tissue within the human body. These stem cells were then coaxed into developing into four specific cell types found in early human embryos:

  1. Epiblast cells, which eventually form the embryo or fetus.
  2. Trophoblast cells, responsible for placental development.
  3. Hypoblast cells, which contribute to the yolk sac.
  4. Extraembryonic mesoderm cells.

These various cell types, a total of 120 cells, were combined in precise ratios, and the researchers observed the remarkable phenomenon as approximately 1% of these cells spontaneously self-assembled into a structure resembling a human embryo.

A Promising Future

While this achievement is ground-breaking, it raises important ethical questions, particularly as these embryo models closely approach the developmental stages of real embryos. The hope is that these models will help scientists gain insights into how various cell types emerge, the initial stages of organ development, and the understanding of inherited or genetic diseases.

Furthermore, there’s the potential to improve in vitro fertilization (IVF) success rates by investigating why some embryos fail to develop or by using the models to test the safety of medicines during pregnancy.

The Road Ahead

While this study is a significant leap forward, it’s essential to address the current 99% failure rate in the assembly of these embryo models. Achieving more consistent results will be vital for understanding miscarriages and infertility fully.

Moreover, as these models come closer to resembling actual embryos, they raise complex ethical questions. Should they be regulated similarly to human embryos, or is a more relaxed approach acceptable? It’s a topic that will likely spark considerable debate.

In summary, this research represents a remarkable milestone in the field of embryo development. It offers a promising pathway for studying the intricate events that lead to the formation of the human body plan, shedding light on a previously enigmatic period of human development. And in the spirit of scientific progress, it encourages us to continue exploring the boundaries of our understanding of life itself.


Want to understand and improve upon your male fertility? Few people realise that 40% of infertilities are due to the male factor! At ExSeed we’ve developed an entirely-at-home sperm test kit, giving you the power to see your sperm cells under the microscope and know your Total Motile Sperm Count, all in the comfort of your own home. Learn more about the ExSeed Sperm Test here.

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More to explore


Wearing tight pants and underwear

Studies show that men who wear looser underwear have higher sperm concentration and total sperm count compared to men who wear tighter underwear. So, lose the tight clothes and wear something loose to give your testicles some air.

CONCLUSION: learn more about how heat can affect sperm quality here.


Besides higher mortality rate and various diseases, stress is associated with low sperm quality. Stress is known to be associated with lower testosterone levels and oxidative stress with both playing an essential role in producing and maintaining healthy sperm cells.

CONCLUSION: If you feel stressed, we recommend you get some help so you can have a balanced mental health. For a stress management guide, download the ExSeed app for free and start your personalized action plan today.

Physical activity

Scientific studies show that men who are physically active have better semen parameters than men who are inactive. Fertility specialists also state that regular physical activity has beneficial impact on sperm fertility parameters and such a lifestyle can enhance the fertility status of men.

Prioritizing exercise can help improve your overall health and result in healthy, fast swimming sperm cells that have good chances of fertilizing an egg.

CONCLUSION: Try incorporating exercise in your weekly schedule to you ensure exercising at least twice weekly. We recommend a combination of cardio training and strength exercise. Read more about exercise and male fertility on our blog.


Fast Food
Processed foods damage the health of sperm-producing cells and cause oxidative stress, which lead to poorer sperm quality. Heavy consumption of junk food (every week) can increase the likelihood of infertility since men who consume vast amounts of unhealthy food are at risk of having poor sperm quality. Besides harming your fertility, junk food enlarges your waistline, harms your cardiovascular system, kidneys, and more.

Eating more fruit and vegetables can increase your sperm concentration and motility. It’s important that you consume a healthy diet filled with antioxidants and that you eat vegetables every day. Foods such as apricots and red bell peppers are high in vitamin A, which improves male fertility by nurturing healthier sperm. Men who are deficient in this vitamin tend to have slow and sluggish sperm.

Sugary snacks/beverages: several times a week Excessive consumption of high sugar items can lead to oxidative stress, which negatively impacts testosterone levels and sperm motility. Sugary snacks and beverages are also highly associated with obesity and low fertility.
CONCLUSION: To boost sperm quality, stay away from fast food, processed food, and sugary snacks or beverages. You need to implement a healthy prudent diet filled with necessary superfoods needed for good sperm production. Check out our guide to Male Fertility Superfoods. For personalized guidance and support on how you can start improving your sperm health, check out the Bootcamp.


Direct heat can inhibit optimal sperm production and cause Sperm DNA damage. Sperm cells like environments that are a couple of degrees lower than body temperature. Avoid overheating from warm blankets, seat warmers, heat from your laptop, hot showers, and saunas.

Cigarette smoking

The exposure to tobacco smoke has significant negative effects on semen quality. The damage of cigarettes and nicotine of course depends on how many cigarettes you smoke per day and for how long, but even low usage (up to 10 cigarettes / day) can inhibit healthy sperm production.  

CONCLUSION: Stay as far away from cigarette smoking as possible if you care about your general health and your fertility. Read more here.

Cell phone

When you have your cell phone in your front pocket, your testicles are exposed to electromagnetic radiation, which studies have shown to damage the sperm cells. Put your phone in the back pocket of your pants or in your jacket pocket.


There is a clear association between obesity and reduced sperm quality. At least part of the reason for this is that obese men may have abnormal reproductive hormonal profiles, which can impair sperm production and lead to infertility. 

A BMI higher than 30 can lead to several processes in the body (overheating, increase in oxidative stress in the testes, sperm DNA damage, erectile dysfunction) that can have a negative impact on male fertility. This can result in problems when trying to conceive.  

CONCLUSION: BMI is one of the risk factors that influence semen quality and, for example, sperm motility.  


A beer or glass of wine now and then do not really harm sperm quality. But excess alcohol drinking (more than 20 units per week) can reduce the production of normally formed sperm needed for a successful pregnancy.

CONCLUSION: If you want to stay safe, stay under 14 units of alcohol per week. For more information on how alcohol can affect male fertility, take a look at our blog: “Alcohol and Sperm Quality”.


Studies show that women younger than 35 and men younger than 40 have a better chance of getting pregnant. Men can produce sperm cells almost through their entire life, but the sperm cell DNA is more fragile and prone to damage after the age of 40.

As men age, their testes tend to get smaller and softer resulting in a decline in sperm quality and production. These changes are partly because of an age-related decrease in testosterone level, which plays a very important role in sperm

production. Higher male age (>40 years) is not only associated with a decline in sperm production but also with increased sperm DNA fragmentation and worsened morphology (shape) and motility (movement). These negative effects make the sperm cells less qualified for egg fertilization.

CONCLUSION: with an age under 40, you shouldn’t have to worry much about age as a factor in itself. However, studies have shown a slow decline after the age of 30-35 years

and if you are above 40 years of age, your sperm quality can be affected due to increased sperm DNA damage resulting in a decrease of sperm motility and concentration. Remember that you cannot evaluate the quality of a sperm sample by just looking at it – this requires a sperm analysis.