It isn’t the easiest task. You must have a beginning, a middle and an end, all in the space of five sentences. It is a nice little exercise to get the writing flowing, and may even help with writers block. “One a day keeps the Writers Block away”?
This was my first attempt:
The lattice structure lay dormant before him, the sheath of sterile cells impregnating every surface. Stretching, moving and oxygenating the growing flesh had taken months, now it quivered in anticipation. Dr. Haverd held his breath as he sent a shock of electricity through the first man made heart. There was a blip, and he sent another shock. His elation escalated as the heart began a steady bu-dum, bu-dum, in its dish.
For some more examples there is a Reddit post about it. Feel free to drop your 5 sentences in the comments.