(1) First thing is to shoot a macro of a flower (these work best) or anything like a leaf with some bokeh and dof.
(2) Then open it in PS and convert to Greyscale
(3) Then, go to Image>Mode>Duotone. A window will pop up and change monotone to Duotone. There, select the second color you want besides white.
Here, I have selected a light blue tone.
(4) Now, is just a case of playing around with the Levels and Contrast until you get the effect you want!
Here is my finished version! :)