A very good question. Actually there are many theories how it was all started.The most common theory is Big Bang which tells us that all universe is condensed in a very small part almost about a atom.And temperature is so much high that atoms can't made.And now there is explosion called Big bang all the matters spread out and it is spreading till now and hence everything forms.But there is a problem wirh this theory a big problem it doesn't tell us what banged?How banged?Why banged?what banged it just sipmly tell us a Bang.But some applications of theory are right which have been proved in LHC. Another Question??
