Compressed Photons = the Big Firecracker
Although very small in size, the Big Firecracker contained all the photons that now make up our Universe.
Since Everything is made of Photons, this pinpoint sized object thus contained, well, Everything.
Consider the Yin and Yang symbol:
http://en.wikipedia.org/wiki/File:Yin_and_Yang.svg
Two very tiny dots, each surrounded by an energy field, and orbiting around each other.
This is a simple conceptual model of a photon, there may be more than two kinds of particles and they are orbiting in 10 or 11 dimensions, but the Universe and everything in it is it made of these. The orbits vary in size and the spinning happens at varying speeds, giving a photon a "frequency." Viewed as it approaches, a photon appears circular, at an angle it traces out a helix, and from the side, it looks like a sine wave.
Although the size of the orbits may very, the particles themselves are probably the same size... VERY VERY tiny. Very! Tiny! So tiny that all of them fit inside a firecracker smaller than a proton.
When ancient boffins lit the Big Firecracker 13.7 (possibly by building a giant accellerator) billion years ago, the photon particles immediately began separating from each other, trying to form traditional photons.
At first there simply was no room for them to do that, so, instead of forming photons, the photonic particles dance around each other in tighter and more compact patterns forming first the very simplest of sub atomic objects, higgs bosons. As the universe becomes larger and larger, more complex objects can be formed, but there is still no room for light.
Finally, after about 10 seconds, the universe was big enough for photons to assume their traditional form, and they began to fly away in all directions at the speed of light, carrying heat away with them, and a few minutes later, the universe is cool enough for atomic nuclei to form.
A nice timeline is here: http://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang