For some, it was his child-like demeanour which made him affable and for some, it was his inspirational vision and work in the field of science which made A.P.J. Abdul Kalam a "universally-loved" Bharat Ratna, who managed to be in politics without being a "politician".
Bollywood celebrities paid heartfelt tributes to the former president, who suddenly passed away on Monday evening in Shillong.
Several names from the Hindi film industry took to Twitter to remember their moments with Kalam, and to bid their 'aakhri salaam'.
Here's what they tweeted:
Amitabh Bachchan: A brilliant mind, a child like demeanour, simple caring and loved by all .. ex POI passes away .. PRAYERS.
Shah Rukh Khan: So sad to hear about the Gurdaspur terror attack & now the news of Dr. Kalam's demise. May Allah bring peace upon all.
Salman Khan: Never had the opportunity to meet Kalam saab but always loved and respected him. As scientist and as president, Kalam saab was a true inspiration for many generations of Indians. When your heart says you should meet someone, don't delay. I always wanted to meet Kalam saab and I should have made the effort. My loss. I will miss Kalam saab. India will miss him.
Priyanka Chopra: "They say Good & Great are seldom in the same man. Dr Kalam was the epitome of both. A big loss for India. May his beautiful soul Rest in Peace."
A.R. Rahman: Dr. Kalam, when you became the president, you gave the word 'hope' a new meaning for Indians... Today, we have lost a great leader who inspired our young minds to feel that we live in the greatest nation on the Earth and that each one of them can achieve great things... May the creator lead you to heaven.
Anupam Kher: Thank you Dr. Kalam for your wisdom, for your inspirational life, for your generosity, for your patriotism & for your teachings. #MyHero
Kabir Bedi: Saluting the memory of APJ Abdul Kalam, India's most loved President, a truly inspirational Bharat Ratna. RIP @APJAbdulKalam.
Sajid Khan: He was in politics,but was never a politician..R.I.P. APJ ABDUL KALAM SAAB...a great human being.
Meiyang Chang: Few people are admired so universally. Thank you Dr. Abdul Kalam for inspiring us. And now you fly on Wings of Fire to your final abode. RIP.
Mohit Chauhan: Dr #Kalam the real rockstar and a true icon for millions of Indians esp the youth... we shall miss ur benign presence and ur vision. RIP sirYou will live in our hearts forever sir. And forever inspire us. RIP Kalam saheb.
Abhishek Bachchan: RIP Dr. Kalam. Huge loss to us all.
Divya Dutta: Not one person Awho's not tweeting abt dr kalam! A truly loved n admired person!! By all! Unanimously!!! Rare n special! RIP sir!
Shreya Ghoshal: Dr. Abdul Kalam inspired millions with his intellect n vision. You taught our nation that knowledge is power. We are indebted to you. RIP.
Neha Dhupia: An author, a teacher, a scientist and one of the best presidents India has ever seen... RIP Dr. APJ Abdul Kalam.
Madhur Bhandarkar: I consider myself fortunate that I had the honor & the privilege of receiving two National Awards at the hands of Shri Abdul Kalam. RIP, Sir.
Kunal Kemmu: A great mind and an inspiration to millions. Keep shining your light from the other side you are our brightest star. APJ Abdul Kalam - RIP.
Farhan Akhtar: Deeply saddened to hear about the demise of one of the most inspirational Indians of our time, former President Dr. APJ Abdul Kalam. RIP.
Ayushmann Khurrana: The silver lining of this era. An epitome of righteousness, intelligence & wisdom. A rare gem. A big loss. Thanks for everything sir. #Kalam.
Anushka Sharma: Very sad to hear about the passing of APJ Abdul Kalam. Loss of an inspiring visionary and a wonderful soul. May his soul RIP.
Sujoy Ghosh: RIP Dr. Kalam. In respect of one the greatest Indian to walk this earth.
Adnan Sami: Dr. APJ Abdul Kalam loved every element of life. Amongst many things, he preached "Unity of Minds through Music". RIP.
Lara Dutta Bhupathi: RIP APJ Kalam. A visionary, a man of honour and Indias pride. Salute! #Respect
Sushmita Sen: What a glorious life!!Greatness lead by example!!#Respect#Salute d life n divine grace of Mr. Avul Pakir Jainulabdeen Abdul Kalam #Godspeed
Manoj Bajpayee: His contribution in putting India on top has been immense incomparable. We bow down to true son of this nation. RIP Kalam sahib!
