Human heart
![In an image representing organ donation, one person's hands give a plastic heart to another person.](https://cdn.mos.cms.futurecdn.net/sneqvUiXyQNiKFccRNgykT-320-80.jpg)
The human heart is a vital organ that pumps blood through the body. You probably don't even think about it, but your heart is always working — it beats about 100,000 times a day, which adds up to about 3 billion beats over an average lifetime. Here's the latest science news about your ticker.
Latest about Heart & Circulation
![microscopic image of bacterial cells full of bright green cholestorol molecules](https://cdn.mos.cms.futurecdn.net/J8VdFyEe42m8VSrVZNPJH-320-80.jpg)
Cholesterol-gobbling gut bacteria could protect against heart disease
By Sneha Khedkar published
Certain microbes in the gut microbiome may guard against heart disease by lowering people's cholesterol.
![Color coded diagram of different cell types within a developing heart on a black background.](https://cdn.mos.cms.futurecdn.net/DKF6UB2ngD9XQ9xCj5qeWE-320-80.jpg)
Never-before-seen cells unveiled in detailed map of developing human heart
By Clarissa Brincat published
The most comprehensive cell "atlas" of the developing human heart to date was crafted using cutting-edge technology and includes never-before-seen cell types.
![Woman checks her pulse while running through a green field.](https://cdn.mos.cms.futurecdn.net/ZvS26e2uEQ6VSmWz4kYBWV-320-80.jpg)
Extreme exercise can pose risks. A cardiologist explains why.
By William Cornwell published
Moderate exercise is good for the heart, but high levels of exercise can cause a phenomenon known as "athletic heart," which comes with risks.
![Illustration of the new heart-on-a-chip depicting a pink heart in the middle of a chip against a blue background](https://cdn.mos.cms.futurecdn.net/84E5RdFxDnpbtExSQAbS7B-320-80.jpg)
Scientists developing new 'heart-on-a-chip'
By Emily Cooke published
So-called heart-on-a-chip systems may enable scientists to evaluate the safety and efficacy of new drugs more accurately than they can with animal tests.
![A researcher holding bags of blood.](https://cdn.mos.cms.futurecdn.net/XuXq3kRNLsMmgxuABBFWDF-320-80.jpg)
What's the rarest blood type?
By Rachael Rettner last updated
Blood typing is particularly important for blood transfusions.
![a close up of a small ice sculpture shaped like a delicate branching blood vessel shown next to a florescent image of cells grown in the same shape](https://cdn.mos.cms.futurecdn.net/DqJHtZ7ZrdK4FLaMvNuEUW-320-80.jpg)
'Ice printing' tiny sculptures could help scientists engineer blood vessels
By Nicoletta Lanese published
A technique for printing 3D structures from ice could be used to help make artificial veins and arteries.
![Photo of a baby lying down in a hospital with wires and medical equipment attached it him. He's holding the hand of an adult whose face is out of frame](https://cdn.mos.cms.futurecdn.net/QfJMo3RQDdJoyCnhxGZZX9-320-80.jpg)
1st partial-heart transplant growing with baby 1 year later
By Nicoletta Lanese published
Heart valves transplanted as part of the first partial-heart transplant in a human are now growing along with the infant who received them.
![Doctor placing a stethoscope on a female patient's chest over the patient's sweater](https://cdn.mos.cms.futurecdn.net/dzcmDpJui9FoCCmvwfoPxM-320-80.jpg)
What is a heart murmur?
By Anna Gora published
Heart murmurs are extra, unusual sounds heard during a heartbeat — but why do they happen?
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