The introduction of naked DNA or other membrane impermeable substances into a cell (transfection) is a ubiquitous problem in cell biology. This problem is particularly challenging when it is desired to load membrane impermeable substances into specific cells, as most transfection technologies (such as liposomal transfection) are based on treating a global population of cells. The technique of optical transfection, using a focused laser to open a small transient hole in the membrane of a biological cell (photoporation) to load membrane impermeable DNA into it, allows individual cells to be targeted for transfection, while leaving neighbouring cells unaffected. Unlike other techniques used to perform single cell transfection, such as microinjection, optical transfection can be performed in an entirely closed system, thereby maintaining sterility of the sample during treatment. Here, we are investigating the introduction and subsequent expression of foreign DNA into living mammalian cells by laser-assisted photoporation with a femtosecond-pulsed titanium sapphire laser at 800 nm, in cells that are adherent.