What do you mean by "pixulation". That's not a term as spelled and is inexact at best in the most likely possible correct spelling.
Normal Photoshop image size enlargement normally uses a technique of interpolation called "Bicubic" resampling, which creates a larger but fuzzy image based on the original, and normally you do not see much evidence of the original pixels in the result. It's just fuzzier.
There are some very sophisticated resampling tools available that can augment Photoshop's capabilities that can yield a better looking result, by attempting to follow lines and edges and keep them sharp. Two such tools, as an example, are OnOne Software's Perfect Resize 7 and Alien Skin's Blow Up 3.
Perhaps you'd be willing to share what it is you're trying to accomplish, then we could give you more specific information about how best to accomplish it.
-Noel
