Here is the inner surface of a red bell pepper (Capsicum annuum). The long thin structures you see here are large individual cells up to 5 mm in length. A new world fruit, the pepper was introduced to Spain in 1493. The mild bell peppers such as this one were developed in the 1920's in Szeged, Hungary.
Equipment used: Canon EOS Rebel T5i with 49 mm long extension tube.