The Nucleofector 2b System (or older generations I or II) works cell type specific kits each of them dedicated to an individual primary cell The Mouse Embryonic Fibroblast Nucleofector Kit 1 is one of our two kits suited for efficient transfection of primary mouse embyonic fibroblasts (MEF) Due to significant diversity between different MEF clones we have developed two Nucleofector Kits (1 and 2) and an easy-to-use Nucleofector Starter Kit to determine which of the 2 kits is optimal for a specific MEF clone The respective cell type-specific Optimized Protocol or recommendation is available under Instructions or in our Lonza Bioscience knowledge database In this Optimized Protocol the best Nucleofection conditions are indicated In addition we share our experience and knowledge for treatment of this cell type