Hold the Tissue!!

Tissue paper once had a purpose in the traditional invitation ensemble. Old printing processes would leave the ink wet on the invitation, so the tissue paper was used to keep the ink from smearing on the card above it. Since then, tissue paper has become more a formality, since its purpose has become obsolete as printing has improved over the many years. So in short, tissue paper isn't necessary. If you're aiming for a traditional ensemble with all the formalities, you will want to include it. But it certainly isn't a must-have for practicality or for etiquette purposes