This isn’t a discovery so much as a great resource (and wonderful source of visuals), but you should really look inside The Cell Image Library… and look inside your cells.
Really. Up close. In living color. Amazing stuff.
Like this, CIL: 3054 – Development of the axon and dendritic arbors in cultured hippocampal neurons after 7 days in vitro.
or this, CIL: 7053 – NIH 3T3 cell expressing EGFP-Lifeact (a small genetically expressed probe that binds to actin and is derived from the first 17 aa of Abp140) imaged with structured illumination.
There are also… videos.