Illustration by Angelika Manhart
I knew I wanted to be a scientist when…

Yin, Yang, Microbiome

By Menghan Liu

When did I know I wanted to be a scientist? I am searching for a past moment, a milestone or a conversation in my head that made me feel like this, but I couldn’t find one.



I was a curious kid. I was curious about nature, animals, as a lot of kids are.

My father, a mathematician, always says he suffered from my childhood curiosities.

He is afraid of rodents. I had a hamster when I was 5. He didn’t step into my room once from the day I got it. Many years later, he still claimed that he had bad dreams during the half year that I had the hamster, and the dreams stopped after it died.

He took me to catch dragonflies right before the summer rainstorms came. Those small beautiful creatures with transparent wings fly so very low before storms. If we ran fast enough, we could trap them in plastic bags.

I wanted to be a biologist.


School in Shandong, China.

But my curiosity didn’t last.

I spent my entire school life in Shandong – the province with the second largest population in China. Every June, 9 million students in Shandong have their future half-decided based on a single three-day test, that decides whether or not they’re going to college. The test is similar to the SAT in the U.S., except that compared to 9 million, there’s only 1.4 million SAT participants each year, and they can take the SAT multiple times.

I went to school from 8 am to 6 pm six days a week. Being in a boarding school for high school means that 7 to 10 pm is also mandatory homework time. Back then I didn’t feel terrible at all since it was the same for all my friends and classmates. Plus, I got good grades.

But something felt weird.

My curiosity was gone. I stopped asking followup questions. All I needed and wanted to do was memorize the textbook, finish my homework and prepare for the big test. I was very anxious about everything.

I didn’t have time to think if I wanted to be a scientist. But I did ok on the test.


2013 – present, New York.

After four years of college majoring in marine biology in the city where I grew up, I came to New York in 2013.

At that time, I realized that I had been anxious in many ways. I was anxious about failing tests, about messing up the marine samples we collected from the sea, about contamination in my cell culture plates, about speaking in public in English.

But studying bioinformatics was a relief. First, I could code alone without talking to anyone. Second, unlike many things in life with no second chance, I could always go back to correct my code.

Then I started to enjoy what I do.

I spent a whole week modeling the battle among different bacteria – ‘killer bacteria’ who produce antibiotics to kill others, ‘resistant bacteria’ who can degrade the antibiotics, ‘cheater bacteria’ who take advantages of the ‘resistant bacteria.’ I used three colors to represent the different bacteria in a short video clip, and watched how red killer bacteria gradually invaded blue resistant bacteria, but eventually were taken over by the purple cheater bacteria.

I had so much fun.

I read the book Missing Microbes, which talks about how overuse of antibiotics could be a huge risk to us and our children. I realized how ignorant I was about the world and what could be the consequences of our daily behaviors. The book is written by Dr. Martin Blaser. He became my Ph.D. mentor.

I am no longer anxious. I realized I only needed to do one thing right, one thing that is important to me.

I made the figures for my first paper. I presented my first poster in Keystone, Colorado. I reanalyzed the American Gut Project (AGP) data which surveyed the gut microbiomes of 9,000 individuals. The founder of the AGP stopped by my poster, gave me some critiques. I started to have collaborations from outside NYU. I published my first paper. I was invited to give talks.

Chinese has a theory of Yin(阴) and Yang(阳), describing how seemingly opposite or contrary forces may actually be complementary, interconnected or even give rise to each other in the natural world.

I start to think that this Yin/Yang idea describes many relationships: between humans and their microbiome, between my past and my present, between me and science.

I still don’t know when I decided that I want to be a scientist. But what I do know is that I want to be one.


Menghan Liu is a graduate student at NYU School of Medicine, with a focus on computational and systems biology. She studies the symbiotic relationship between humans and the good bugs in our guts.