Nucleoside-modified Messenger RNA (mRNA) is a special type of molecule that is made up of only four different building blocks. These building blocks are called nucleosides. The job of mRNA is to carry instructions from our DNA to the parts of the cell that make proteins. Proteins are special molecules in our body that help make things work.
Scientists have figured out a way to modify the nucleosides in mRNA so that they can be used to make proteins outside of the cell. Basically, they make tiny changes to the building blocks so that they can be used to tell a cell how to make a specific protein. This is very useful for medicine because it can help us make certain types of proteins which can then be used to treat diseases.