A nanosecond is a billionth of a second and a picosecond is a trillionth. In practice, though, "picosecond" is a category label rather than a specification: cleared devices fire roughly 240 to 900 picosecond pulses, against about 5 to 20 nanoseconds for a Q-switched laser. The real gap is ten to forty times, not a thousand.
Older lasers work mainly by heating pigment until it fractures. A picosecond pulse is delivered so quickly that it adds a mechanical effect: the target is shattered rather than only cooked. With a lens array fitted, the pulse can also create tiny cavities within the skin, which triggers a repair response without removing the surface.
Less heat spilling into surrounding tissue is the practical consequence, and it is the reason recovery tends to be shorter than with more thermal approaches.
Coloured tattoo ink. Blue, green and yellow clear better with picosecond lasers than with older ones. One trial found about a third of picosecond-treated tattoos reaching 75% clearance, against roughly one in seven with the older laser.
Acne scarring. In a head-to-head against a common 1550 nm fractional laser, picosecond scored better on a standard scarring assessment.
These are real, published advantages. If either is what you are treating, the technology is doing something for you.
Black tattoo ink. Picosecond and nanosecond performed about the same. If your tattoo is plain black, the newer machine may not shorten your course.
General brown pigment and sun spots. No clear superiority has been demonstrated over older nanosecond lasers. Both work; neither has been shown to be better.
Melasma. A meta-analysis found no significant benefit, and picosecond lasers are not cleared for it. Melasma is easily provoked by heat and is usually better served by topical treatment and oral options.
This depends on the wavelength used more than on the brand of machine.
That comparison comes from a study of two different machines with different optics, so it is not purely a wavelength effect.
Treated pigment typically darkens for a few days and flakes off over one to two weeks. That is expected.
Pico Genesis is not a device. It is a treatment protocol run on the enlighten laser. Being quoted for it is fine — just know you are comparing a technique against device names, which is not like for like.
Some devices offer both modes. At least one laser in this class can fire either picosecond or nanosecond pulses, with the operator choosing. So "I had a pico laser" does not guarantee every pulse was picosecond. It is a fair question to ask.
If you get cold sores, tell your provider. Laser treatment can reactivate the virus, and antiviral medication started in advance is the standard precaution.