Can you mix enzymes to make a yummy treat? Learn more about yeasts and microbes by creating your own living, breathing, sourdough starter. Gather a jar, flour, water, a fork and a breathable lid for this bubbly challenge with Librarian Davey.

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STEM Challenge is created by San Francisco Public Library from the Youth Librarian STEM team. Stay STEM-tastic by reading, learning and experimenting at home.

In response to feedback from our Black community and staff, we updated the original name STEM Challenge Yo’Self to STEM Challenge on July 19, 2021. We recognize the original title is appropriated from Black vernacular and perpetuates racism, and has caused harm to our Black/BIPOC community members and staff. Our library is working towards being an anti-racist institution and committed to doing better.