perhaps you just didnt learn the lesson well
Einstein came up with this
http://en.wikipedia.org/wiki/Mass-energy_equivalence , it shows that you can convert matter into energy and viceversa, this has been experimentally confirmed specifically in nuclear reactions.
You can look at this part from the link I posted, if you have further doubts pay a visit to the physics department of the closest university. Or give them a call, I am sure they will be happy to give a short explanation.
But all of this is ACADEMIC because what follows next is that you say "ok fine you may destroy matter into energy" but you cant create things that were not there before (be that matter or energy)....so SOMEONE "surely" put the energy and mass that we see in the universe. To answer the "where did all this come from" you have to go into even more esoteric parts of physics and for this you need very advanced math that you (nor I) are familiar with, its in essence very technical and not something the layman can say "SHOW ME" and there will be a demonstration of the creation of the Universe (besides the theories are very much in flux)
From the wikipedia article:
A little while later, the first
transmutation reactions (such as
[12] the
Cockcroft-Walton experiment: 7Li +
p → 2 4He) verified Einstein's formula to an accuracy of ±0.5%. In 2005, Rainville et al. published a direct test of the energy-equivalence of mass lost in the binding-energy of a neutron to atoms of particular isotopes of silicon and sulfur, by comparing the mass-lost to the energy of the emitted gamma ray associated with the neutron capture. The binding mass-loss agreed with the gamma ray energy to a precision of ±0.00004 %, the most accurate test of E=mc2 to date.
[3] The mass–energy equivalence formula was used in the development of the
atomic bomb. By measuring the mass of different
atomic nuclei and subtracting from that number the total mass of the
protons and
neutrons as they would weigh separately, one gets the exact
binding energy available in an
atomic nucleus. This is used to calculate the energy released in any
nuclear reaction, as the difference in the total mass of the nuclei that enter and exit the reaction.