You're looking at a microscopic "submarine" made by German micromechanics firm microTEC. The 4 mm length by 0.65 mm diameter sub is small enough to cruise through an artery, powered by a propeller that can be activated by an external magnetic field. The device is designed to be injected into the human body to transport drugs and make repairs.

From Eye of Science gallery (by the way, a fantastic website):

Colored scanning electron micrograph (SEM) of a micro-submarine made
by the microTEC company, in Duisburg, Germany. After the specifications of the submarine were entered into a computer, a reservoir of an acrylic liquid was then solidified by a computer-controlled laser. The beam caused the liquid to polymerize and solidify as it passed through, building up the submarine in layers about 10 micrometer thick. The RMPD (Rapid Micro Product Development) process allows tiny components to be made cheaply and accurately. This submarine measures around 4 millimeters in length and 0,65 millimeters in diameter. It is hoped that tiny machines such as this may one day be used for detecting and repairing defects in the human body. Magnification: 17 X.

This is from the year 2000: anyone knows what's the latest news on this?

Links: Eye of Science | microTEC's website | old Time Magazine article