According to the earlier reports, Samsung Galaxy S4 could feature a HD 4.99 inch Amoled screen which could allow pixel density of up to 440 PPI. Even though, this density is really sharp and attractive, But it's a lot similar to the densities of new Sony and HTC phones. So, Samsung in order to make Samsung Galaxy S4's display different from its rivals is working upon higher pixel densities. According to a report, Samsung is experiment upon hexagonal and diamond shaped pixels. Which in result provide them with their target of achieving pixel density greater than 440 PPI.
However, this enlargement of pixels is made possible by Laser induced thermal imaging which allows a place for sub-pixels; this technique is cheap, but, found some problems initially. Now, the issues are resolved and green signal has been given to this technique. So, Samsung would be first one to apply it and we have to wait and see how it works when Galaxy S4 emerges into the market.