Here's why:

* Ribosomes are the protein factories of the cell. They read the genetic code carried by mRNA and use it to assemble amino acids into proteins.

* mRNA is a messenger molecule. It carries the genetic instructions from DNA in the nucleus to the ribosomes in the cytoplasm.

So, the journey of mRNA goes like this:

1. Transcription: DNA is transcribed into mRNA in the nucleus.

2. mRNA transport: mRNA travels out of the nucleus and into the cytoplasm.

3. Translation: mRNA reaches a ribosome and is translated into a protein.