it was molecular structure of DNA this was appeared 1n April 1953 Watson and Crick presented the structure of DNA- Helix.it carried the genetic information. the DNA Molecule shaped in twisted ladder. Franklin produced an X- ray photograph. DNA structure is made of molecules called nucleotide. Watson and crick also work on 3-D structure of DNA. this mark the history in molecular biology to understanding the genes control and genetic information. They also work on cell. They use stick and ball to understand to test their idea.