The idea of "peak experiences" was created by psychologist Abraham Maslow in the mid-20th century. Such experiences inspire feelings of intense happiness. They are said to give you a sense that you're one with all of creation.
I've had a few peak experiences. The one I think about the most happened about 20 years ago. At the time I lived in the southwest desert of the United States. About an hour from our home was a small lake called Whitewater Draw where tens of thousands of Sandhill cranes spend the winter. Sandhill cranes are the oldest living bird species, going back at least 2.5 million years. I used to go visit them every year.
On this particular visit, the cranes had come in for their afternoon siesta. Thousands of them were gathered around the little lake. All of a sudden, they all took off at the same time, lifting up to fill the sky overhead. The other few visitors and I gasped. We stood stock-still, watching 10,000 cranes circle above our heads, calling to each other with their million-year-old croak. In that moment, I felt like there was no separation between me and them.
When the birds started to settle back down, the other visitors and I all looked at each other in amazement and then smiled the same smile. For that brief time, there was no separation between us, either.