Node.js uses a default memory limit for its heap (the space where JavaScript objects are stored), and if your application uses more memory than this limit, the process will crash with an 'out of memory' error. To fix this, you can increase the heap size using the `--max-old-space-size` flag, which allows Node to allocate more memory. For example, running `node --max-old-space-size=4096 app.js` will increase the memory limit to 4GB. However, increasing memory isn’t always the best solution, as it only delays the problem. It’s important to profile your app and identify memory leaks or inefficiencies that cause excessive memory usage. Tools like `clinic` or `v8-profiler` can help pinpoint the source of memory bloat.