• libuv
• There is only one thread
• Event loop runs in that one thread
• Async work done by async I/O interfaces provided by most operating systems. Only when that is not available does node fallback to a thread pool (with 4 threads).
• Event Loop Phases:
  1. Timers
  2. IO Callbacks
  3. IO Polling
  4. Set Immediate
  5. Close Events