In late November of 1991, a 3-year-old girl was diagnosed with leukemia. There was a 30 percent chance she would die.
In the coming months, she would receive a long list of chemotherapy drugs: 6MP, asparaginase, methotrexate, prednisone, and vincrinstine. The miracle was not only that these drugs could potentially cure her, but that they existed at all.
In his fantastic book, The Emperor of All Maladies, author and physician Sid Mukherjee explains the history of cancer and how brilliant physicians and scientists finally began to discover cures for the disease.
You see, for many years, doctors and scientists dreamed of finding a single cure for all cancers. They searched for a radical surgery or a miracle drug that could cure everything from breast cancer to leukemia to prostate cancer. According to Mukherjee, however, breakthroughs finally came when scientists stopped trying to tackle this large scale problem and made the problem smaller.
The first breakthrough came when Sidney Farber, now known as the Father of Modern Chemotheraphy, decided to focus exclusively on treating leukemia. He was one of the first physicians to dedicate his efforts solely to a single type of cancer and by narrowing his focus Farber was able to make significant progress against this single condition.
Eventually, the drugs and treatments Farber uncovered for leukemia led to new solutions for other cancers. By focusing on one tiny vertical, Farber uncovered answers that could be used to treat the larger problem. As Mukherjee put it, "[By] focusing microscopically on a single disease, one could extrapolate into the entire universe of diseases." 
This central idea, that solving large complex problems is often accomplished by first attacking smaller micro-problems, is useful not just for cancer treatments, but for life in general.
How to Solve Complex Problems
The main lesson mentioned above is simple: When you're facing a complex problem or trying to do something bold, start with a smaller version of the larger problem. Focus exclusively on that small problem and solve it. Use the answers to this small issue to expand your knowledge of the larger issue. Repeat.
If you take a look around, you can see this pattern playing out everywhere.
For example, consider Amazon. The company started by selling books. Once they mastered the online purchase and delivery process of books, they moved on to other products. Today, they sell just about everything.
Amazon could have started by trying to solve the big problem: How do we master digital commerce? Instead, they started with a narrow focus and expanded from there. It has been proven many times that this small-to-large approach works well for businesses, and I think it can be very useful for our personal goals as well.
The Idea in Practice
Let's consider a few examples of how we might put this idea into practice.
Creativity. BIG PROBLEM: How do I become more creative?
Small solution: If you want to become a good photographer, then start small. Learn how to take a really good picture of a chair. Once you can take a fantastic picture of a chair, use those principles -- light, composition, lines, curves -- to take better pictures of everything.
Exercise. BIG PROBLEM: How can I start exercising consistently?
Small solution: If you can't crack the fitness code and struggle to exercise consistently, then forget about every other exercise and just learn how to do one pushup. Use the steps I describe here to increase your number slowly. Stick with that one exercise for days, weeks, months. Once you prove to yourself that you can solve this small problem, use the lessons you learn to become more consistent at exercise in general.
Nutrition. BIG PROBLEM: How can I eat healthy each day?
Small solution: Want to improve your nutrition? Maybe you should ignore switching to a new diet at first. You don't need to change all of your food habits at once. You could start by solving a very small segment of the problem: eat one vegetable today. Master that. Do it for four weeks. Or longer. Take what you learn about being consistent with that one thing and apply it to adding a second healthy food.
Narrowing your focus is a mental model that you can apply whenever you want to start a new behavior or take on a new project that seems too big or overwhelming or complex to handle. It is a filter you can run larger problems through to approach issues from a more useful place.
So, how do you solve big problems? Start with a smaller one.
That 3-year-old girl who was diagnosed with leukemia and treated with the drugs that were discovered through the Father of Chemotherapy, Sidney Farber? It was my sister. More than 20 years later, she is alive and well.
I'm very glad Farber decided to start small.
James Clear writes at JamesClear.com, where he shares science-based ideas for living a better life and building habits that stick. To get strategies for boosting your mental and physical performance by 10x, join his free newsletter.
This article was originally published on JamesClear.com.