The Sphere

Step 1.

Create a new 800X800 pixels document with the white background. Go to channels palette and create a new channel (Alfa 1). Choose the Rectangular Marquee Tool and holding Shift make a 25X25 pixels selection (apply Window > Info to see a size).

Step 2.

Set a foreground color as white and fill a selection (ALT+Backspace). Apply Select > Modify > Contract (contract by 2 pixels) and press Del. Move the selection 2 pixels up and 2 pixels left. Now apply Edit > Define Pattern (pattern 1). Go to the layers palette and create a new layer (Layer 1). Press Ctrl+A and fill the layer by your pattern (apply Edit > Fill...).

Step 3.

Go to the channels palette and apply a button "Load Channel as Selection". Go to the layers palette and create a new layer (Layer 2). Set a foreground color as black and fill a selection (ALT+Backspace). Press Ctrl+D to deselect a selection. Now delete a Layer 1.

Step 4.

Choose the Elliptical Marquee Tool and holding Shift make a big circle. Apply Filter > Distort > Spherize with Amount->100%. Apply Select > Inverse and press Del. Press Ctrl+D to deselect a selection. Then change the size of the document. Apply Image > Image Size (400X400 pixels). And that's it.