Science Friday Your Cells Are Always Building A Whole New You
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Jan 1, 2026 
Alejandro Sánchez Alvarado, a leading biologist and chief scientific officer at the Stowers Institute, delves into the fascinating world of regeneration using planarians. They can regrow an entire body from just a fragment! He discusses the surprising limits of this regeneration, the significance of cellular turnover versus chronological age, and the potential for regenerative medicine to address diseases like Alzheimer's. With humor and optimism, Alejandro inspires a fresh outlook on our own cellular renewal in the New Year.
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You Are A Continuously Renewing Body
- Our bodies constantly remake themselves at the cellular level throughout life.
- By 2027 you will have replaced a mass of cells equal to your entire body weight.
Worms That Laugh At Knives
- Planarians have been studied for ~300 years and withstand being sliced repeatedly.
- Almost every fragment containing ~5,000–8,000 cells can regenerate into a whole animal.
A Dirty Fountain Launched a Lab Line
- Alejandro Sánchez Alvarado and his team trapped planarians in Montjuïc fountains, finding them in a trash-filled fountain.
- That collection launched the laboratory line they still use today.